Science.gov

Sample records for american continental shelf

  1. 78 FR 36571 - North American Datum of 1983 (NAD 83) Outer Continental Shelf (OCS) Provisional Official...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-06-18

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF THE INTERIOR Bureau of Ocean Energy Management North American Datum of 1983 (NAD 83) Outer Continental Shelf (OCS) Provisional Official Protraction Diagram (OPDs) AGENCY: Bureau of Ocean Energy Management (BOEM),...

  2. 76 FR 2919 - Outer Continental Shelf Official Protraction Diagram and Supplemental Official Outer Continental...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-01-18

    ... Bureau of Ocean Energy Management, Regulation and Enforcement Outer Continental Shelf Official Protraction Diagram and Supplemental Official Outer Continental Shelf Block Diagrams AGENCY: Bureau of Ocean... American Datum of 1983 (NAD 83) Outer Continental Shelf Official Protraction Diagram and...

  3. Direct observations of American eels migrating across the continental shelf to the Sargasso Sea

    PubMed Central

    Béguer-Pon, Mélanie; Castonguay, Martin; Shan, Shiliang; Benchetrit, José; Dodson, Julian J.

    2015-01-01

    Since inferring spawning areas from larval distributions in the Sargasso Sea a century ago, the oceanic migration of adult American eels has remained a mystery. No adult eel has ever been observed migrating in the open ocean or in the spawning area. Here, we track movements of maturing eels equipped with pop-up satellite archival tags from the Scotian Shelf (Canada) into the open ocean, with one individual migrating 2,400 km to the northern limit of the spawning site in the Sargasso Sea. The reconstructed routes suggest a migration in two phases: one over the continental shelf and along its edge in shallow waters; the second in deeper waters straight south towards the spawning area. This study is the first direct evidence of adult Anguilla migrating to the Sargasso Sea and represents an important step forward in the understanding of routes and migratory cues. PMID:26505325

  4. Direct observations of American eels migrating across the continental shelf to the Sargasso Sea.

    PubMed

    Béguer-Pon, Mélanie; Castonguay, Martin; Shan, Shiliang; Benchetrit, José; Dodson, Julian J

    2015-01-01

    Since inferring spawning areas from larval distributions in the Sargasso Sea a century ago, the oceanic migration of adult American eels has remained a mystery. No adult eel has ever been observed migrating in the open ocean or in the spawning area. Here, we track movements of maturing eels equipped with pop-up satellite archival tags from the Scotian Shelf (Canada) into the open ocean, with one individual migrating 2,400 km to the northern limit of the spawning site in the Sargasso Sea. The reconstructed routes suggest a migration in two phases: one over the continental shelf and along its edge in shallow waters; the second in deeper waters straight south towards the spawning area. This study is the first direct evidence of adult Anguilla migrating to the Sargasso Sea and represents an important step forward in the understanding of routes and migratory cues. PMID:26505325

  5. Coastal Carbon Synthesis for the Continental Shelf of the North American Pacific Coast (NAPC)

    NASA Astrophysics Data System (ADS)

    Siedlecki, S. A.; Alin, S. R.

    2015-12-01

    The West Coast represents the longest coastline in North America, stretching from Panama all the way northward to the Aleutians. Key advances in the carbon cycling of this margin have been made since the North American Continental Margins report (Hales et al., 2008), notably the convergence of models and observations on air-sea fluxes; more sophisticated coastal carbon cycle models; and increased observational coverage in space and time, allowing for more data synthesis and model-data comparison. The coast was divided up into sub-regions based on differences in oceanographic drivers of coastal carbon cycling. Those sub-regions include the Gulf of Alaska, the Central American Isthmus, and the California Current System (CCS), which is further subdivided into northern, central, and southern sectors. The carbon budget for the Pacific Coast of North America identifies the best-known fluxes as the air-sea exchange of CO2 and terrestrial inputs. The least constrained fluxes include respiration, cross-shelf exchange, and carbon metabolism in estuaries. Spatial trends were typically consistent among models and observations, but the magnitude of the fluxes varied widely. While more modeling and observational studies exist than are presented here, relevant fluxes for the carbon budget were often unreported. In the long-term, investments in research and monitoring will be needed to better constrain the fluxes of many of the highly variable regions described in this study. In addition to the budget, this synthesis identifies gaps and priorities for future research.

  6. 76 FR 54787 - Outer Continental Shelf Official Protraction Diagram, Lease Maps, and Supplemental Official Outer...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-09-02

    ... Bureau of Ocean Energy Management, Regulation and Enforcement Outer Continental Shelf Official Protraction Diagram, Lease Maps, and Supplemental Official Outer Continental Shelf Block Diagrams AGENCY... revised North American Datum of 1927 (NAD 27) Outer Continental Shelf Official Protraction Diagram,...

  7. Coordination: Southeast continental shelf studies

    SciTech Connect

    Menzel, D.W.

    1989-01-26

    The objective of this investigation is to obtain model descriptions of the flow modifications in the Southeast Atlantic continental shelf due to Gulf Stream fluctuations and topographic effects. 2 refs., 4 figs.

  8. Chriolepis prolata, a new species of Atlantic goby (Teleostei: Gobiidae) from the North American continental shelf.

    PubMed

    Hastings, Philip A; Findley, Lloyd T

    2015-01-01

    A new species of seven-spined goby of the genus Chriolepis is described from five specimens collected from the continental shelf of the northeastern Gulf of Mexico and Atlantic Ocean off South Carolina in depths of ca 54 to 110 m. The "Platform Goby", Chriolepis prolata, is distinguishable from all other western Atlantic species currently assigned to the genus Chriolepis and the morphologically similar genus Varicus in having pelvic-fin rays one through four branched, the fifth (innermost) pelvic-fin ray unbranched and relatively long (longer than the second ray to longer than all other pelvic-fin rays); most lateral body scales ctenoid, extending anteriorly in a wedge to a level anterior to the first dorsal-fin insertion or nearly to the pectoral-fin axil, with two or more rows of small cycloid scales extending anteriorly to near the pectoral-fin axil, cycloid scales along the bases of the dorsal and anal fins, and no scales on the belly; and the first two anal-fin pterygiophores inserted anterior to the first haemal spine. It closely resembles C. bilix but differs from that species which has a scaled belly, a shorter fifth pelvic-fin ray, prolonged dorsal-fin spines and smaller teeth in the lower jaw. An earlier report of C. bilix from Florida waters apparently refers to C. prolata.  PMID:25660803

  9. Modeling the dynamics of continental shelf carbon.

    PubMed

    Hofmann, Eileen E; Cahill, Bronwyn; Fennel, Katja; Friedrichs, Marjorie A M; Hyde, Kimberly; Lee, Cindy; Mannino, Antonio; Najjar, Raymond G; O'Reilly, John E; Wilkin, John; Xue, Jianhong

    2011-01-01

    Continental margin systems are important contributors to global nutrient and carbon budgets. Effort is needed to quantify this contribution and how it will be modified under changing patterns of climate and land use. Coupled models will be used to provide projections of future states of continental margin systems. Thus, it is appropriate to consider the limitations that impede the development of realistic models. Here, we provide an overview of the current state of modeling carbon cycling on continental margins as well as the processes and issues that provide the next challenges to such models. Our overview is done within the context of a coupled circulation-biogeochemical model developed for the northeastern North American continental shelf region. Particular choices of forcing and initial fields and process parameterizations are used to illustrate the consequences for simulated distributions, as revealed by comparisons to observations using quantitative statistical metrics. PMID:21329200

  10. Continental shelf nurseries and recruitment variability in American plaice and yellowtail flounder on the Grand Bank: insights into stock resiliency

    NASA Astrophysics Data System (ADS)

    Walsh, Stephen J.; Simpson, Mark; Morgan, M. Joanne

    2004-05-01

    In 1994, a directed fishing moratorium was declared for Grand Bank American plaice ( Hippoglossoides platessoides) and yellowtail flounder ( Limanda ferruginea) stocks because both stocks showed severe declines in abundance from heavy exploitation during the mid 1980s and early 1990s. Four years later, the fishery for yellowtail re-opened while the plaice stock has shown little recovery and the moratorium is still in effect. To assess the possible causes of the differences in recovery between species, we examined the spatial structure and environmental characteristics of the continental shelf nursery habitats of plaice and yellowtail, and their relationship to recruitment variability and overall population size. Depth plays a major influential role determining the spatial pattern and the abundance of juveniles of both species and in the case of plaice the spatial structure of the adult population also determines the amount of nursery area utilised by juveniles. Recruitment variability was higher in plaice than in yellowtail. We found year class synchrony in both species indicating that common environmental conditions and/or biological processes are affecting recruitment in a similar manner. Density-dependent regulation appears to be more severe in yellowtail and this should contribute to a more stable population when compared to plaice. These results are discussed in terms of resiliency of both stocks to over-exploitation.

  11. Coordination: southeast continental shelf studies. Progress report

    SciTech Connect

    Menzel, D.W.

    1981-02-01

    The objectives are to identify important physical, chemical and biological processes which affect the transfer of materials on the southeast continental shelf, determine important parameters which govern observed temporal and spatial varibility on the continental shelf, determine the extent and modes of coupling between events at the shelf break and nearshore, and determine physical, chemical and biological exchange rates on the inner shelf. Progress in meeting these research objectives is presented. (ACR)

  12. 26 CFR 1.638-1 - Continental Shelf areas.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 26 Internal Revenue 7 2012-04-01 2012-04-01 false Continental Shelf areas. 1.638-1 Section 1.638-1...) INCOME TAXES (CONTINUED) Continental Shelf Areas § 1.638-1 Continental Shelf areas. (a) General rule. For.... The terms Continental Shelf of the United States and Continental Shelf of a possession of the...

  13. 26 CFR 1.638-1 - Continental Shelf areas.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 26 Internal Revenue 7 2011-04-01 2009-04-01 true Continental Shelf areas. 1.638-1 Section 1.638-1...) INCOME TAXES (CONTINUED) Continental Shelf Areas § 1.638-1 Continental Shelf areas. (a) General rule. For.... The terms Continental Shelf of the United States and Continental Shelf of a possession of the...

  14. 26 CFR 1.638-1 - Continental Shelf areas.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 26 Internal Revenue 7 2013-04-01 2013-04-01 false Continental Shelf areas. 1.638-1 Section 1.638-1...) INCOME TAXES (CONTINUED) Continental Shelf Areas § 1.638-1 Continental Shelf areas. (a) General rule. For.... The terms Continental Shelf of the United States and Continental Shelf of a possession of the...

  15. 26 CFR 1.638-1 - Continental Shelf areas.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 26 Internal Revenue 7 2010-04-01 2010-04-01 true Continental Shelf areas. 1.638-1 Section 1.638-1...) INCOME TAXES (CONTINUED) Continental Shelf Areas § 1.638-1 Continental Shelf areas. (a) General rule. For.... The terms Continental Shelf of the United States and Continental Shelf of a possession of the...

  16. 26 CFR 1.638-1 - Continental Shelf areas.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 26 Internal Revenue 7 2014-04-01 2013-04-01 true Continental Shelf areas. 1.638-1 Section 1.638-1...) INCOME TAXES (CONTINUED) Continental Shelf Areas § 1.638-1 Continental Shelf areas. (a) General rule. For.... The terms Continental Shelf of the United States and Continental Shelf of a possession of the...

  17. 75 FR 61512 - Outer Continental Shelf Official Protraction Diagrams

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-10-05

    ... Bureau of Ocean Energy Management, Regulation and Enforcement Outer Continental Shelf Official... Outer Continental Shelf Official Protraction Diagrams (OPDs) located within Atlantic Ocean areas, with... informational purposes only. Outer Continental Shelf Official Protraction Diagrams in the North Atlantic,...

  18. 76 FR 63654 - Outer Continental Shelf Official Protraction Diagram, Lease Maps, and Supplemental Official Outer...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-10-13

    ... Bureau of Ocean Energy Management Outer Continental Shelf Official Protraction Diagram, Lease Maps, and Supplemental Official Outer Continental Shelf Block Diagrams AGENCY: Bureau of Ocean Energy Management (BOEM), Interior. ACTION: Availability of revised North American Datum of 1927 (NAD 27) Outer Continental...

  19. Freshwater peat on the continental shelf

    USGS Publications Warehouse

    Emery, K.O.; Wigley, R.L.; Bartlett, A.S.; Rubin, M.; Barghoorn, E.S.

    1967-01-01

    Freshwater peats from the continental shelf off northeastern United States contain the same general pollen sequence as peats from ponds that are above sea level and that are of comparable radiocarbon ages. These peats indicate that during glacial times of low sea level terrestrial vegetation covered the region that is now the continental shelf in an unbroken extension from the adjacent land areas to the north and west.

  20. Freshwater peat on the continental shelf.

    PubMed

    Emery, K O; Wigley, R L; Bartlett, A S; Rubin, M; Barghoorn, E S

    1967-12-01

    Freshwater peats from the continental shelf off northeastern United States contain the same general pollen sequence as peats from ponds that are above sea level and that are of comparable radiocarbon ages. These peats indicate that during glacial times of low sea level terrestrial vegetation covered the region that is now the continental shelf in an unbroken extension from the adjacent land areas to the north and west. PMID:17801856

  1. Pollen and palynofacies analyses of Paleocene-Eocene Thermal Maximum sediments from the North American continental shelf

    NASA Astrophysics Data System (ADS)

    Willard, D. A.; Robinson, M. M.; Self-Trail, J. M.; Wandless, G. A.; Sluijs, A.

    2014-12-01

    Analyses of pollen and palynofacies from Paleocene-Eocene Thermal Maximum (PETM) sediments from three cores collected on the Atlantic Coastal Plain provide insights into the timing of vegetation and hydrologic changes associated with the PETM in eastern North America. The Mattawoman Creek-Billingsley Road (MCBR2), South Dover Bridge (SDB), and Bass River (ODP Site 1074AX) cores were collected at progressively greater distances from the paleoshoreline in continental shelf deposits in Maryland and New Jersey, USA. The PETM carbon isotope excursion (CIE) at each site is accompanied by sharp increases in pollen and spore concentrations, as well as changes in terrestrial palynomorph assemblage composition. In the two sites proximal to the paleoshoreline in Maryland, CIE fern spore abundance was two- to three times greater than in pre-CIE assemblages. At the distal site at Bass River, fern spores are present in CIE sediments and absent in pre-CIE sediments. Angiosperm pollen is most common in CIE sediments at all three sites. Palynofacies analyses, which quantify contributions of organic material from marine and non-marine sources, indicate that terrestrial influx increased sharply at the CIE onset. This observation is consistent with seasonally increased runoff from the continent.

  2. 49 CFR 192.10 - Outer continental shelf pipelines.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 49 Transportation 3 2013-10-01 2013-10-01 false Outer continental shelf pipelines. 192.10 Section... shelf pipelines. Operators of transportation pipelines on the Outer Continental Shelf (as defined in the Outer Continental Shelf Lands Act; 43 U.S.C. 1331) must identify on all their respective pipelines...

  3. 49 CFR 192.10 - Outer continental shelf pipelines.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 49 Transportation 3 2011-10-01 2011-10-01 false Outer continental shelf pipelines. 192.10 Section... shelf pipelines. Operators of transportation pipelines on the Outer Continental Shelf (as defined in the Outer Continental Shelf Lands Act; 43 U.S.C. 1331) must identify on all their respective pipelines...

  4. 49 CFR 192.10 - Outer continental shelf pipelines.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 49 Transportation 3 2014-10-01 2014-10-01 false Outer continental shelf pipelines. 192.10 Section... shelf pipelines. Operators of transportation pipelines on the Outer Continental Shelf (as defined in the Outer Continental Shelf Lands Act; 43 U.S.C. 1331) must identify on all their respective pipelines...

  5. 49 CFR 192.10 - Outer continental shelf pipelines.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 49 Transportation 3 2012-10-01 2012-10-01 false Outer continental shelf pipelines. 192.10 Section... shelf pipelines. Operators of transportation pipelines on the Outer Continental Shelf (as defined in the Outer Continental Shelf Lands Act; 43 U.S.C. 1331) must identify on all their respective pipelines...

  6. 49 CFR 192.10 - Outer continental shelf pipelines.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 49 Transportation 3 2010-10-01 2010-10-01 false Outer continental shelf pipelines. 192.10 Section... shelf pipelines. Operators of transportation pipelines on the Outer Continental Shelf (as defined in the Outer Continental Shelf Lands Act; 43 U.S.C. 1331) must identify on all their respective pipelines...

  7. Coordination: southeast continental shelf studies. Progress report

    SciTech Connect

    Menzel, D.W.

    1980-03-01

    The GABEX I experiment is designed to provide synoptic coverage of a series of Gulf Stream wave-like disturbances, the effect of these on the circulation of the entire shelf, and on biological and chemical processes. This study was initiated in February 1980 when current meter arrays were deployed. These meters will be removed in July 1980. In April three ships will simultaneously study the effects of Gulf Stream disturbances on the hydrography, chemistry, and biology of the shelf. One vessel will track a specific wave-like disturbance and provide synoptic coverage of the shelf area. The second vessel will determine the effect of shelf break processes on adjacent shelf water; and the third will study trace metal distributions in and outside of disturbances. Research progress is reported in continental shelf studies, nearshore and estuarine studies (diffusion of freshwater out of nearshore zone), tidal currents and material transport, and mixing of inlet plumes.

  8. Coordination: Southeast Continental Shelf studies. Progress report

    SciTech Connect

    Menzel, D.W.

    1981-02-01

    An overview of the Oceanograhic Program of Skidaway Institute of Oceanograhy is presented. Included are the current five year plan for studies of the Southeast Continental Shelf, a summary of research accomplishments, proposed research for 1981-1982, current status of the Savannah Navigational Light Tower, and a list of publications. (ACR)

  9. Elephant teeth from the atlantic continental shelf

    USGS Publications Warehouse

    Whitmore, F.C., Jr.; Emery, K.O.; Cooke, H.B.S.; Swift, D.J.P.

    1967-01-01

    Teeth of mastodons and mastodons have been recovered by fishermen from at least 40 sites on the continental shelf as deep as 120 meters. Also present are submerged shorelines, peat deposits, lagoonal shells, and relict sands. Evidently elephants and other large mammals ranged this region during the glacial stage of low sea level of the last 25.000 years.

  10. 49 CFR 195.9 - Outer continental shelf pipelines.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 49 Transportation 3 2011-10-01 2011-10-01 false Outer continental shelf pipelines. 195.9 Section... HAZARDOUS LIQUIDS BY PIPELINE General § 195.9 Outer continental shelf pipelines. Operators of transportation pipelines on the Outer Continental Shelf must identify on all their respective pipelines the specific...

  11. 75 FR 1076 - Outer Continental Shelf Civil Penalties

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-01-08

    ... Minerals Management Service Outer Continental Shelf Civil Penalties AGENCY: Minerals Management Service.... SUMMARY: The Outer Continental Shelf Lands Act requires the MMS to review the maximum daily civil penalty assessment for violations of regulations governing oil and gas operations in the Outer Continental Shelf...

  12. 49 CFR 195.9 - Outer continental shelf pipelines.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 49 Transportation 3 2014-10-01 2014-10-01 false Outer continental shelf pipelines. 195.9 Section... HAZARDOUS LIQUIDS BY PIPELINE General § 195.9 Outer continental shelf pipelines. Operators of transportation pipelines on the Outer Continental Shelf must identify on all their respective pipelines the specific...

  13. 49 CFR 195.9 - Outer continental shelf pipelines.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 49 Transportation 3 2012-10-01 2012-10-01 false Outer continental shelf pipelines. 195.9 Section... HAZARDOUS LIQUIDS BY PIPELINE General § 195.9 Outer continental shelf pipelines. Operators of transportation pipelines on the Outer Continental Shelf must identify on all their respective pipelines the specific...

  14. 49 CFR 195.9 - Outer continental shelf pipelines.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 49 Transportation 3 2013-10-01 2013-10-01 false Outer continental shelf pipelines. 195.9 Section... HAZARDOUS LIQUIDS BY PIPELINE General § 195.9 Outer continental shelf pipelines. Operators of transportation pipelines on the Outer Continental Shelf must identify on all their respective pipelines the specific...

  15. 49 CFR 195.9 - Outer continental shelf pipelines.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 49 Transportation 3 2010-10-01 2010-10-01 false Outer continental shelf pipelines. 195.9 Section... HAZARDOUS LIQUIDS BY PIPELINE General § 195.9 Outer continental shelf pipelines. Operators of transportation pipelines on the Outer Continental Shelf must identify on all their respective pipelines the specific...

  16. Fisheries and oil development on the continental shelf

    SciTech Connect

    Benner, C.S.; Middleton, R.W.

    1991-01-01

    The title of this volume is misleading because it has not clearly defined the geographic limits of the continental shelf. However, a glance at the Contents makes it clear that the contributions to this symposium are restricted to some shelf areas of the continental USA and especially to the Beaufort Sea off the north coast of Alaska. These papers were derived from presentations at the 119th annual meeting of the American Fisheries Society held in Anchorage, Alaska, in 1989. An awareness of the geographic scope of this symposium helps to put its contents into better focus. It is apparent that a broad coverage of fisheries, oil development, and its probable consequences from a global or even North American perspective is not provided. With the exception of the first 38 pages covering a broad range of topics, the remaining 134 pages are devoted exclusively to the Beaufort Sea.

  17. Iceberg scouring on the Norwegian continental shelf

    SciTech Connect

    Lien, R.

    1983-05-01

    This paper is a condensed version of parts of a Dr. ing. thesis to be presented during 1983. The first part of the paper deals with the regional distribution of iceberg scouring on the Norwegian continental shelf, and some general aspects related to it. The second part deals with iceberg scouring as a local phenomenon and its relation to the sea floor topography, sediment distribution, and geological and geotechnical properties of the sediments.

  18. LINKAGE BETWEEN PRODUCTION AND RESPIRATION ON THE LOUISIANA CONTINENTAL SHELF.

    EPA Science Inventory

    Abstract for presentation. Original title, "PRIMARY PRODUCTION, BACTERIOPLANKTON PRODUCTION, AND COMMUNITY RESPIRATION IN STRATIFIED WATERS OF THE NORTHERN GULF OF MEXICO CONTINENTAL SHELF: LINKAGE TO HYPOXIA."

  19. 75 FR 72679 - Renewable Energy Alternate Uses of Existing Facilities on the Outer Continental Shelf-Acquire a...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-11-26

    ... Federal Register on July 9, 2008 (73 FR 39376). The North American Industry Classification System (NAICS... Energy Alternate Uses of Existing Facilities on the Outer Continental Shelf--Acquire a Lease... an Outer Continental Shelf (OCS) renewable energy lease. We are taking this action because...

  20. 76 FR 8962 - Renewable Energy Alternate Uses of Existing Facilities on the Outer Continental Shelf-Acquire a...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-02-16

    ... published in the Federal Register on July 9, 2008 (73 FR 39376). The North American Industry Classification... Energy Alternate Uses of Existing Facilities on the Outer Continental Shelf--Acquire a Lease... acquisition of an Outer Continental Shelf (OCS) renewable energy lease. We are taking this action because...

  1. Sonography of a glaciated continental shelf

    NASA Astrophysics Data System (ADS)

    Loncarevic, B. D.; Courtney, R. C.; Fader, G. B. J.; Giles, P. S.; Piper, D. J. W.; Costello, G.; Hughes Clarke, J. E.; Stea, R. R.

    1994-08-01

    Sonographs of the inner continental shelf off Halifax, Nova Scotia, show a large part of the inner shelf area consisting of exposed bedrock in which the inferred sequence of structural events is clearer than the record on land. Ribbed moraines overlie eroded drumlins and provide new information on the deglaciation history. Morphologic features allow a precise definition of the maximum postglacial lowstand of sealevel at -65 to -70 m. A 1000 km2 area in eastern Canada was surveyed with a multibeam sounder EM100, manufactured by Simrad of Norway. A 100% coverage of the sea floor was achieved with 50 to 100 m track spacing, and position control was achieved using the differential global positioning system (DGPS) with an accuracy of 1-2 m. Data were corrected for ship motion, gridded at a 10 m spacing, and displayed as obliquely illuminated relief image. The sonograph revealed characteristics of the sea bed in detail for the interpretation of bedrock and surficial structures and processes. The bathymetric images may be more useful for geologic mapping than air photographs and satellite images on nearby land, where vegetation commonly obscures the geologic features.

  2. Oceanology of the antarctic continental shelf: Volume 43

    SciTech Connect

    Jacobs, S.S.

    1985-01-01

    This book discusses the seas of the deep continental shelf, which play an important climatic role in sea ice production, deep ocean ventilation and wastage of the Antarctic ice sheet. This volume includes analyses of measurements taken from ships and satellites, and from sea ice and glacial ice. High resolution profiling equipment, long term bottom-moored instruments, continuous remote sensors, geochemical tracers and computer models have provided the basis for new insights into the continental shelf circulation. Color plates and an accompanying GEBCO Circum-Antarctic map effectively portray the continental shelf in relation to the glaciated continent, the sea ice and the surrounding Southern Ocean.

  3. Petroleum potential of northern Australian Continental Shelf

    SciTech Connect

    Smith, M.R.; Ross, J.G.

    1986-11-01

    A study of the publicly available data from the offshore northern Australian continental shelf has shown that three prospective sedimentary sequences are present. A Cenozoic basin possibly containing Miocene reefal carbonates exists in the west part of the region, a structurally distinct Mesozoic basin containing thick sandstone intervals underlies the Cenozoic, and a thick paleozoic basin, possibly containing Devonian reefs and younger Paleozoic sandstone intervals, lies southeast of the Aru Archipelago and east of a north-northeast-trending ridge located along the eastern edges of the Aru and Timor Troughs. Paleozoic sediments also underlie the Mesozoic west of this ridge. The cenozoic and Mesozoic basins and the western Paleozoic subbasin are separated by major sequence boundaries. All the basins present hydrocarbon potential to a greater or lesser extent. The Mesozoic basin will probably be the prime target for exploration over the next few years, but secondary objectives in Cenozoic and Paleozoic sediments should not be ignored. The numerous different play types identified in this study, the positive signs from exploration in the early 1970s, the recent neighboring discoveries, and improvements in seismic data quality provide an incentive for oil companies to conduct detailed exploration of the area. 7 figures.

  4. Outer Continental Shelf Oil and Gas Leasing/Production Program

    SciTech Connect

    Not Available

    1988-01-01

    This annual report on the Outer Continental Shelf (OCS) Oil and Gas Leasing and Production program summarizes receipts and expenditures, and includes information on OCS safety violations as reported by the US Coast Guard. 3 figs., 12 tabs.

  5. Manganese, Iron, and sulfur cycling in Louisiana continental shelf sediments

    EPA Science Inventory

    Sulfate reduction is considered the primary pathway for organic carbon remineralization on the northern Gulf of Mexico Louisiana continental shelf (LCS) where bottom waters are seasonally hypoxic, yet limited information is available on the importance of iron and manganese cyclin...

  6. Phytoplankton Communities in Louisiana coastal waters and the continental shelf

    EPA Science Inventory

    Louisiana coastal waters and the adjacent continental shelf receive large freshwater and nutrient inputs from the Mississippi and Atchafalaya Rivers, creating favorable conditions for increased phytoplankton productivity. To examine inshore-offshore patterns in phytoplankton comm...

  7. Sediment metabolism on the Louisiana continental shelf - Eldridge

    EPA Science Inventory

    Rates of aerobic and anaerobic sediment metabolism were measured on the Louisiana Continental Shelf during 5 cruises in 2006 and 2007. On each cruise, 3-4 stations were occupied in regions of the shelf that experience summer bottom-water hypoxia. Net DIC, O2, N2, and nutrient f...

  8. Crescentic dunes on the inner continental shelf off northern California

    USGS Publications Warehouse

    Cacchione, D.A.; Field, M.E.; Drake, D.E.; Tate, G.B.

    1987-01-01

    These dunes appear to be migrating obliquely to the regional shelf gradient; a preferred offshore direction of tranpsort is indicated by the extended southern wings of many dunes. Over longer time periods (decades), the seaward transport of fine to medium sand in the crescentic dunes is probably an important way by which sand escapes the shallow part of the continental shelf in this region and mixes with the muddy deposits of the central shelf. -from Authors

  9. Glacial morphology and depositional sequences of the Antarctic Continental Shelf

    USGS Publications Warehouse

    ten Brink, U.S.; Schneider, Christopher

    1995-01-01

    Proposes a simple model for the unusual depositional sequences and morphology of the Antarctic continental shelf. It considers the regional stratal geometry and the reversed morphology to be principally the results of time-integrated effects of glacial erosion and sedimentation related to the location of the ice grounding line. The model offers several guidelines for stratigraphic interpretation of the Antarctic shelf and a Northern Hemisphere shelf, both of which were subject to many glacial advances and retreats. -Authors

  10. Macrofaunal production along the UK continental shelf

    NASA Astrophysics Data System (ADS)

    Bolam, S. G.; Barrio-Frojan, C. R. S.; Eggleton, J. D.

    2010-10-01

    Estimates of secondary production ( P/ B ratio and total production) by macrobenthic communities across the UK continental shelf are presented. Values for individual sampling stations varied from 0.21 to 4.1 y - 1 for community P/ B and 3.1 to 897.2 kJ m - 2 y - 1 for total production. Such data fills an important gap pertaining to our understanding of the spatial variation in production estimates for this region. Benthic production estimates varied primarily at small (inter-station) scales (24 nm), although larger-scale differences were observed. In general, the highest production estimates were exhibited by benthic communities in Cardigan Bay (Irish Sea) and East English Channel, while the lowest estimates were observed for the mid- and northern North Sea areas. The former were typified by shallow, gravelly areas of seabed which exhibit high bed tidal stress and do not thermally stratify during the summer months. On average, annelids contribute an overwhelming majority of the total production with different regions varying in the relative contributions from other phyla such as molluscs, crustaceans and echinoderms. Spatial heterogeneity of sediment granulometric variables occurred primarily between stations while those of other variables (e.g., depth, stratification, and tidal bed stress) were more regional. Although a large proportion of the spatial variation in secondary production estimates was not explained by environmental characteristics, the data indicate that such relationships are scale-dependent. Average bed temperature was a significant factor in creating some of the observed differences at large spatial scales. The possible reasons why a larger proportion of the variation in production estimates was not explained by the present study are presented.

  11. Sea surface height trend and variability at seasonal and interannual time scales in the Southeastern South American continental shelf between 27°S and 40°S

    NASA Astrophysics Data System (ADS)

    Saraceno, Martin; Simionato, Claudia G.; Ruiz-Etcheverry, Laura A.

    2014-12-01

    Recent improvements in satellite altimetry data correction terms are encouraging studies of the remote sensed sea level anomalies (SLA) progressively closer to the coast and over shallow continental shelves. In this paper we describe and discuss the SLA trend and variability at seasonal and interannual time scales in the southeastern South American continental shelf influenced by the Río de la Plata estuary and the Patos Lagoon fresh waters. The spatio-temporal coverage of the gridded altimetry SLA data allows identify several variability patterns and the associated physical processes. On seasonal time scales, the combination of the solar radiation and wind forcing cycles accounts for up to 98% of the variability. Seasonal variability of the wind is responsible for a difference of up to 16 cm between the southern (Argentinean) Río de la Plata estuary coast and the Uruguayan and southern Brazilian coasts. On interannual time scales, positive/negative SLA anomalies are coherent with El Niño/La Niña events. Finally, a significant positive trend of up to 5 mm yr-1 is found in all the study area except in the region around the Patos Lagoon (Brazil) and part of the Río de la Plata. Besides the local relevance of the results, this study indicates that satellite altimetry data are accurate enough to unveil SLA spatio-temporal patterns close to the coast and over continental shelves in the mentioned time scales.

  12. In search of the Malaysian Extended Continental Shelf

    NASA Astrophysics Data System (ADS)

    Yahaya, N. A. Z.; Musa, T. A.; Omar, K. M.; Din, A. H. M.; Abdullah, N. M.; Othman, A. H.; Wahab, M. I. A.

    2016-06-01

    Over the years, the sovereignty proclamation of Coastal States for their extended continental shelf has been a crucial matter. The declaration and extension of a continental shelf under the United Nations Convention on the Law of the Sea provide significant potential for many developing nations in economics, trades, resource exploitation, communication and security. Hence, the application of satellite altimeter, as one of the solutions for collecting bathymetry data to define the approximate limits of the continental shelf, is reviewed. This paper also discusses the possible significance or contribution of space-derived bathymetry, i.e. the seafloor topography, either independently or harmoniously with different datasets, to meet the element of the Article 76 of UNCLOS.

  13. Seals map bathymetry of the Antarctic continental shelf

    NASA Astrophysics Data System (ADS)

    Padman, Laurie; Costa, Daniel P.; Bolmer, S. Thompson; Goebel, Michael E.; Huckstadt, Luis A.; Jenkins, Adrian; McDonald, Birgitte I.; Shoosmith, Deborah R.

    2010-11-01

    We demonstrate the first use of marine mammal dive-depth data to improve maps of bathymetry in poorly sampled regions of the continental shelf. A group of 57 instrumented elephant seals made on the order of 2 × 105 dives over and near the continental shelf on the western side of the Antarctic Peninsula during five seasons, 2005-2009. Maximum dive depth exceeded 2000 m. For dives made near existing ship tracks with measured water depths H<700 m, ˜30% of dive depths were to the seabed, consistent with expected benthic foraging behavior. By identifying the deepest of multiple dives within small areas as a dive to the seabed, we have developed a map of seal-derived bathymetry. Our map fills in several regions for which trackline data are sparse, significantly improving delineation of troughs crossing the continental shelf of the southern Bellingshausen Sea.

  14. Continental shelf fish production estimation from CZCS chlorophyll data

    NASA Technical Reports Server (NTRS)

    Iverson, Richard L.

    1989-01-01

    A method for ocean fish production estimation was proposed for development. The method was to use data acquired with the Coastal Zone Color Scanner, and processed into chlorophyll concentrations by the GSFC ocean Sciences Division, in combination with fish production and primary production data acquired from different ocean areas. A linear relation exits between annual fish production and annual phytoplankton carbon production for a wide range of coastal ocean environments. The uses of several existing algorithms which relate primary production to CZCS chlorophyll data as input to the fish production regression model is proposed. A question relating phytoplankton production to CZCS chlorophyll was obtained by Eppley (1984) using chlorophyll data obtained from field samples, equivalent to chlorophyll data obtained from CZCS imagery, and primary production data obtained from ship-board observations on a wide variety of coastal and open ocean environments. This equation was modified with additional data and was successfully tested using CZCS data and field chlorophyll and phytoplankton production data obtained from northeastern North American continental shelf waters and Atlantic open ocean waters. The modified Eppley (1984) relation also estimated phytoplankton annual carbon production in the Sargasso Sea within the confidence limits of a mean value obtained from the Eppley (1984) equation for oceanic waters that provide about 90 percent of total ocean primary production. The modified Eppley production formula applied to CZCS chlorophyll data obtained from several northeastern North American coastal environments gave phytoplankton annual carbon production values similar to the values used in the fish production regression equation.

  15. Circulation and exchange processes over the continental shelf and slope

    SciTech Connect

    Csanady, G.T.

    1988-01-01

    The theme of the work during the past triennium has been the SEEP experiment, data interpretation and modeling related to the goals of the experiment, and was characterized by increasing cooperation with colleagues from other disciplines. The theoretical contributions dealt with shelf-slope interaction, the dynamics and climatology of currents over the continental slope, and the behavior of fate of organic particles. Observational papers discussed various exchange mechanisms at the shelf edge, with special attention to particle exchange, and the quiescence of currents over the mid continental slope which is presumably responsible for the accumulation of organic particles.

  16. Uncovering the glacial history of the Irish continental shelf (Invited)

    NASA Astrophysics Data System (ADS)

    Dunlop, P.; Benetti, S.; OCofaigh, C.

    2013-12-01

    In 1999 the Irish Government initiated a €32 million survey of its territorial waters known as the Irish National Seabed Survey (INSS). The INSS is amongst the largest marine mapping programmes ever undertaken anywhere in the world and provides high-resolution multibeam, backscatter and seismic data of the seabed around Ireland. These data have been used to provide the first clear evidence for extensive glaciation of the continental shelf west and northwest of Ireland. Streamlined drumlins on the mid to outer shelf record former offshore-directed ice flow towards the shelf edge and show that the ice sheet was grounded in a zone of confluence where ice flowing onto the shelf from northwest Ireland merged with ice flowing across the Malin Shelf from southwest Scotland. The major glacial features on the shelf are well developed nested arcuate moraine systems that mark the position of the ice sheet margin and confirm that the former British Irish Ice Sheet was grounded as far as the shelf edge around 100 km offshore of west Donegal at the last glacial maximum. Distal to the moraines, on the outermost shelf, prominent zones of iceberg plough marks give way to the Barra/Donegal fan and a well developed system of gullies and canyons which incise the continental slope. Since 2008 several scientific cruises have retrieved cores from the shelf and slope to help build a more detailed understanding of glacial events in this region. This presentation will provide an overview of the glacial history of the Irish shelf and will discuss ongoing research programmes that are building on the initial research findings to produce a better understanding of the nature and timing of ice sheet events in this region.

  17. Outer Continental Shelf Environmental Assessment Program: comprehensive bibliography, January 1988

    SciTech Connect

    Not Available

    1988-01-01

    The bibliography lists reports from investigators of the Alaska Outer Continental Shelf Environmental Assessment Program. Some non-program documents are also included. More than 3600 entries are sorted by author and citation number. Cross-references are available by Alaska region, discipline and research unit number.

  18. Microbial Communities in Sediments across the Louisiana Continental Shelf

    EPA Science Inventory

    The Louisiana continental Shelf (LCS) is a dynamic system that receives discharges from two large rivers. It has a stratified water column that is mixed by winter storms, hypoxic bottom water from spring to fall, and a muddy seafloor with highly mixed surficial sediments. Spatia...

  19. Coastal zone and Continental Shelf conflict resolution: improving ocean use and resource dispute management

    SciTech Connect

    Nyhart, J.D.; Harding, E.T.

    1985-11-01

    Contents include: An overview of coastal zone and continental shelf conflicts; Experience in coastal zone management conflict; Future coastal zone conflicts; Outer continental shelf conflicts; Georges Bank and Gulf of Maine; and Future considerations.

  20. 77 FR 15382 - Outer Continental Shelf Scientific Committee; Notice of Renewal

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-03-15

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF THE INTERIOR Outer Continental Shelf Scientific Committee; Notice of Renewal AGENCY: Bureau of Ocean Energy... the Outer Continental Shelf (OCS) Scientific Committee (Committee). The Committee provides advice...

  1. 76 FR 43230 - Outer Continental Shelf Air Regulations Consistency Update for Virginia

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-07-20

    ... From the Federal Register Online via the Government Publishing Office ENVIRONMENTAL PROTECTION AGENCY 40 CFR Part 55 Outer Continental Shelf Air Regulations Consistency Update for Virginia AGENCY... Outer Continental Shelf (OCS) Air Regulations. Requirements applying to OCS sources located within...

  2. 75 FR 10809 - Outer Continental Shelf (OCS) Scientific Committee-Notice of Renewal

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-03-09

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF THE INTERIOR Outer Continental Shelf (OCS) Scientific Committee--Notice of Renewal AGENCY: Minerals Management Service (MMS), Interior. ACTION: Notice of renewal of the Outer Continental Shelf Scientific...

  3. Down-welling circulation of the northwest European continental shelf: A driving mechanism for the continental shelf carbon pump

    NASA Astrophysics Data System (ADS)

    Holt, Jason; Wakelin, Sarah; Huthnance, John

    2009-07-01

    Annually integrated measurements of pCO2 have demonstrated that seasonally stratified regions of temperate shelf seas can be an important sink of atmospheric CO2. A key process to support this sink is the transport of carbon from shelf seas to below the permanent pycnocline of the deep ocean. Using a hydrodynamic model simulation of the northwest European Continental shelf, we find that both the large scale circulation and frictional processes support the off-shelf transport of carbon sufficiently quickly to remove ˜40% of the carbon sequestered by one growing season before the onset of the next. This transport is highly heterogeneous, with some regions being only weakly flushed. Only 52% of this exported carbon is transported below the permanent pycnocline, hence the shelf sea and open ocean carbon cycles are intrinsically coupled.

  4. Geochemistry of sediments of the western Canadian continental shelf

    NASA Astrophysics Data System (ADS)

    Macdonald, R. W.; Pedersen, T. F.

    1991-08-01

    Few chemical data exist for the sedimentary environment off the Canadian west coast. Here we define the chemical nature of the shelf sediments by examining the important sources of material (natural and anthropogenic) to the region and processes relevant to diagenesis. Slightly more data exist for the continental shelf to the south (Washington) and north (Alaska), however it is clear that the sedimentary environment of these neighbouring shelves differs importantly from the Canadian portion. The British Columbia shelf receives little modern terrigenous detritus due mainly to isolation from terrestrial sediment sources by fiords, inland seas, or bypassing by shelf canyons. The chemical state of the sediments depends on the rate of supply of material, the energy of the depositional or erosional environment and the organic and inorganic composition of the material. These features in concert with bottom water characteristics control the redox state. Although no basins hosting continuous depositional records for the Holocene on the open British Columbia shelf have been identified or studied in a manner described by BUCKLEY ( Continental Shelf Research, 11, 1099-1122), some coastal embayments and fiords provide valuable historical records of post-glacial sedimentation. Such environments will prove to be increasingly useful in future studies of changes in regional climate and in establishing the chronology of natural disasters and anthropogenic impacts. Recommendations are given for a variety of research projects that would help us to understand better both chemical interactions at the seabed and Late Quaternary depositional history.

  5. 78 FR 4167 - Commercial Wind Lease Issuance on the Atlantic Outer Continental Shelf Offshore Delaware

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-01-18

    ... Bureau of Ocean Energy Management Commercial Wind Lease Issuance on the Atlantic Outer Continental Shelf... Availability of a Commercial Lease of Submerged Lands for Renewable Energy on the Outer Continental Shelf... (Bluewater) for an area of the Outer Continental Shelf (OCS) offshore Delaware. The purpose of this notice...

  6. 26 CFR 1.1402(a)-12 - Continental shelf and certain possessions of the United States.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 26 Internal Revenue 12 2012-04-01 2012-04-01 false Continental shelf and certain possessions of... Income § 1.1402(a)-12 Continental shelf and certain possessions of the United States. (a) Certain... amounts are excluded from gross income under section 931. (b) Continental shelf. For the definition of...

  7. 26 CFR 1.1402(a)-12 - Continental shelf and certain possessions of the United States.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 26 Internal Revenue 12 2014-04-01 2014-04-01 false Continental shelf and certain possessions of... Income § 1.1402(a)-12 Continental shelf and certain possessions of the United States. (a) Certain... amounts are excluded from gross income under section 931. (b) Continental shelf. For the definition of...

  8. 26 CFR 301.9001 - Statutory provisions; Outer Continental Shelf Lands Act Amendments of 1978.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 26 Internal Revenue 18 2013-04-01 2013-04-01 false Statutory provisions; Outer Continental Shelf... Rules Application of Internal Revenue Laws § 301.9001 Statutory provisions; Outer Continental Shelf Lands Act Amendments of 1978. Section 302 of the Outer Continental Shelf Lands Act Amendments of...

  9. 26 CFR 1.1402(a)-12 - Continental shelf and certain possessions of the United States.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 26 Internal Revenue 12 2010-04-01 2010-04-01 false Continental shelf and certain possessions of....1402(a)-12 Continental shelf and certain possessions of the United States. (a) Certain possessions. For... from gross income under section 931. (b) Continental shelf. For the definition of the term...

  10. 26 CFR 301.9001 - Statutory provisions; Outer Continental Shelf Lands Act Amendments of 1978.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 26 Internal Revenue 18 2010-04-01 2010-04-01 false Statutory provisions; Outer Continental Shelf... Rules Application of Internal Revenue Laws § 301.9001 Statutory provisions; Outer Continental Shelf Lands Act Amendments of 1978. Section 302 of the Outer Continental Shelf Lands Act Amendments of...

  11. 26 CFR 301.9001 - Statutory provisions; Outer Continental Shelf Lands Act Amendments of 1978.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 26 Internal Revenue 18 2012-04-01 2012-04-01 false Statutory provisions; Outer Continental Shelf... Rules Application of Internal Revenue Laws § 301.9001 Statutory provisions; Outer Continental Shelf Lands Act Amendments of 1978. Section 302 of the Outer Continental Shelf Lands Act Amendments of...

  12. 26 CFR 1.1402(a)-12 - Continental shelf and certain possessions of the United States.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 26 Internal Revenue 12 2013-04-01 2013-04-01 false Continental shelf and certain possessions of... Income § 1.1402(a)-12 Continental shelf and certain possessions of the United States. (a) Certain... amounts are excluded from gross income under section 931. (b) Continental shelf. For the definition of...

  13. 26 CFR 301.9001 - Statutory provisions; Outer Continental Shelf Lands Act Amendments of 1978.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 26 Internal Revenue 18 2011-04-01 2011-04-01 false Statutory provisions; Outer Continental Shelf... Rules Application of Internal Revenue Laws § 301.9001 Statutory provisions; Outer Continental Shelf Lands Act Amendments of 1978. Section 302 of the Outer Continental Shelf Lands Act Amendments of...

  14. 26 CFR 301.9001 - Statutory provisions; Outer Continental Shelf Lands Act Amendments of 1978.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 26 Internal Revenue 18 2014-04-01 2014-04-01 false Statutory provisions; Outer Continental Shelf... Rules Application of Internal Revenue Laws § 301.9001 Statutory provisions; Outer Continental Shelf Lands Act Amendments of 1978. Section 302 of the Outer Continental Shelf Lands Act Amendments of...

  15. 76 FR 2254 - Notice of Arrival on the Outer Continental Shelf

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-01-13

    ... Arrival (NOA) on the Outer Continental Shelf in the Federal Register (74 FR 29439). We received two sets... established on March 4, 1982, as part of a final rule entitled, Outer Continental Shelf Activities (47 FR 9366... SECURITY Coast Guard 33 CFR Part 146 RIN 1625-AB28 Notice of Arrival on the Outer Continental Shelf...

  16. 26 CFR 1.1402(a)-12 - Continental shelf and certain possessions of the United States.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 26 Internal Revenue 12 2011-04-01 2011-04-01 false Continental shelf and certain possessions of... Income § 1.1402(a)-12 Continental shelf and certain possessions of the United States. (a) Certain... amounts are excluded from gross income under section 931. (b) Continental shelf. For the definition of...

  17. 77 FR 57572 - Notice of Arrival on the Outer Continental Shelf

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-09-18

    ... of Arrival (NOA) on the Outer Continental Shelf (OCS) final rule [Docket No. USCG-2008-1088] (76 FR... SECURITY Coast Guard Notice of Arrival on the Outer Continental Shelf AGENCY: Coast Guard, DHS. ACTION... Continental Shelf (OCS). The Coast Guard NOA-OCS program currently requires NOA information for those...

  18. 75 FR 18404 - Safety Zone; FRONTIER DISCOVERER, Outer Continental Shelf Drillship, Chukchi and Beaufort Sea...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-04-12

    ... Continental Shelf Drillship, Chukchi and Beaufort Sea, Alaska'' in the Federal Register (75 FR 803). The NPRM... various prospects located in the Chukchi and Beaufort Sea Outer Continental Shelf, Alaska, during the 2010... off the northern coast in the Beaufort Sea Outer Continental Shelf, Alaska, during the 2010...

  19. 76 FR 79705 - Information Collection Activities: Operations in the Outer Continental Shelf for Minerals Other...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-12-22

    ... the Outer Continental Shelf for Minerals Other than Oil, Gas, and Sulphur; Submitted for Office of..., ``Operations in the Outer Continental Shelf for Minerals Other than Oil, Gas, and Sulphur''. DATES: Submit... Continental Shelf for Minerals other than Oil, Gas, and Sulphur. OMB Control Number: 1014-NEW. Abstract:...

  20. 77 FR 15118 - Information Collection Activities: Operations in the Outer Continental Shelf for Minerals Other...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-03-14

    ... Continental Shelf for Minerals Other Than Oil, Gas, and Sulphur; Submitted for Office of Management and Budget... Continental Shelf for Minerals Other than Oil, Gas, and Sulphur. This notice also provides the public a second... 282, Operations in the Outer Continental Shelf for Minerals Other than Oil, Gas, and Sulphur....

  1. Heat flow of the Norwegian continental shelf

    NASA Astrophysics Data System (ADS)

    Pascal, Christophe

    2015-04-01

    Terrestrial heat flow influences a large collection of geological processes. Its determination is a requirement to assess the economic potential of deep sedimentary basins. Published heat flow calculations from e.g. major oil provinces are however seldom. Robust heat flow determinations in drillholes require logging of undisturbed temperatures and intensive sampling of core material for petrophysical measurements. Temperature logging in exploration drillholes is traditionally conducted during drill breaks or shortly after drilling, resulting in temperatures severely disturbed by mud circulation and coring is restricted to selected intervals. Alternatively, test temperatures, information from electric logs and lithological descriptions of drill cuttings can be used to overcome these limitations. The present contribution introduces new heat flow determinations based on 63 exploration drillholes from the Norwegian North Sea, the Mid Norway Margin and the Barents Shelf. Our analyses are based on released DST temperatures, precise lithological descriptions of drill cuttings, previously measured rock matrix thermal conductivities and established porosity laws. Our results suggest median heat flow values of 64 mW/m2, 65 mW/m2 and 72 mW/m2 for the North Sea, the Mid Norway Margin (mainly the Trøndelag Platform) and the SW Barents Shelf respectively. The Barents Shelf shows significantly high heat flow, suggesting lateral transfer of heat from the mantle of the adjacent young ocean. In detail, heat flow increases by ~ 10 mW/m2 from the southern Norwegian North Sea towards the Mid Norway Margin. This result appears to be in very good agreement with seismic tomographic studies suggesting northward thinning of the underlying mantle lithosphere. Our results together with published marine heat flow data from the Mid Norway Margin suggest a gradual decrease in heat flow levels from both the North Sea and the Trøndelag Platform towards the centres of the deep Møre and V

  2. Continental shelf waves on the Alborán sea

    NASA Astrophysics Data System (ADS)

    Serrano, M. A.; Díez-Minguito, M.; Ortega-Sánchez, M.; Losada, M. A.

    2015-12-01

    The existence of free continental shelf waves in the Western Mediterranean Sea is studied using a statistical approach. Hourly mean sea level at six locations extended along the northern and southern coast of the Alborán Sea were analyzed by standard correlation and spectral analysis techniques for two periods of 91 and 92 days, respectively. The mean sea level was adjusted for the effect of atmospheric pressure according to the hydrostatic approximation. The wind-coherent response of sea level was removed by calculating the transfer function between the input alongshore wind stress and the output adjusted sea level. The cross-correlation analyses indicate time lags that are consistent with the hypothesis of the propagation of the free shelf waves predicted by the continental shelf wave theory. The presence of a westward-travelling signal on the NCS and a west-to-east travelling signal on the SCS of the Alborán Sea is confirmed. The cross spectra between residual sea level at the six locations show significant coherence at long periods. For these periods, the phase difference spectra show that the directions of propagation of the free waves are consistent with the interpretation of the cross correlation analysis. There is evidence of a seasonal variation in the phase speed of the waves, which may be related to variations in the speeds of currents in the Alborán Sea. The observations suggest the presence of continental shelf waves on both coasts of the Alborán Sea.

  3. The geomorphology of a glaciated continental shelf, Western Scotland, UK

    NASA Astrophysics Data System (ADS)

    Howe, John; Dove, Dayton; Bradwell, Tom

    2013-04-01

    We present recently collected swath bathymetry and legacy seismic data from two regions of the north-west UK continental shelf: the Sea of the Hebrides; and the Firth of Lorn, western Scotland. Both regions have experienced extensive Pleistocene ice sheet glaciation and both provide abundant geomorphological evidence of subglacial and postglacial processes. The Sea of the Hebrides bathymetry data cover 2200 km2 and provide new geomorphological evidence for an ice stream flowing from western Scotland and the Inner Hebrides focusing towards a trough-mouth fan (the Barra Fan) at the continental shelf break during the height of the last glaciation. Notably, bedrock structures provide a control on the location and orientation of glacially overdeepened basins and troughs on the inner shelf. Whilst around the Islands of Canna and Rum, convergent seabed glacial lineations and other subglacially streamlined features eroded in bedrock preserve the direction of ice sheet movement - indicating ice streaming in a south-westerly direction across the continental shelf. We propose that this fast-flow zone formed part of a larger convergent ice stream system draining much of western Scotland and the north of Ireland. The Firth of Lorn bathymetry acquisition comprises 553km2 of data, collected as part of the INIS Hydro program (Ireland, Northern Ireland and Scotland Hydrographic Survey). This region of nearshore continental shelf is revealed as predominantly bedrock-dominated seabed, characterised by a series of narrow, strongly fault-controlled troughs, part of the Great Glen Fault Zone complex. Evidence for glaciation is widespread and well preserved in the Firth of Lorn and surrounding seabed with moraines, bedrock lineations (?megagrooves?) and overdeepened basins common across the area. Initial mapping shows that our understanding of the configuration and style of deglaciation in these sectors of the former British-Irish Ice Sheet can be greatly improved by the collection of

  4. Structure and development of the southern Moroccan continental shelf

    USGS Publications Warehouse

    Dillon, William P.

    1974-01-01

    The structure of the continental shelf off southern Morocco was studied by means of 2,100 km of seismic reflection profiles, magnetic and bathymetric surveys, and dredge samples. The research area lies off four geologic divisions adjacent to the coast: the Atlas Mountains; the Souss Trough; the Anti-Atlas Mountains; and the Aaiun Basin. The continental shelf, along with the western Atlas Mountains, the western Souss Trough, and the entire Aaiun Basin, has subsided along a normal fault-flexure system. This system runs along the shore at the Anti-Atlas Mountains, and cuts off this cratonic block from the shelf subsidence. The shelf is narrow and characterized by out-building off the Anti-Atlas range, whereas it is broader and characterized by upbuilding to the north and south. Deposition was essentially continuous at least from Early Cretaceous through Eocene time. Published work suggests that the last cycle of sedimentation began during Permian rifting. After Eocene time, most sediments carried to the shelf must have bypassed it and gone to construct the slope and rise or to the deep sea. Tertiary orogenies caused extensive folding of Mesozoic and early Tertiary deposits off the Atlas Mountains. ?? 1974.

  5. Heat Flow of the Norwegian Continental Shelf

    NASA Astrophysics Data System (ADS)

    Pascal, C.

    2015-12-01

    Terrestrial heat flow determination is of prime interest for oil industry because it impacts directly maturation histories and economic potential of oil fields. Published systematic heat flow determinations from major oil provinces are however seldom. Robust heat flow determinations in drillholes require logging of undisturbed temperatures and intensive sampling of core material for petrophysical measurements. Temperature logging in exploration drillholes is traditionally conducted during drill breaks or shortly after drilling, resulting in temperatures severely disturbed by mud circulation and coring is restricted to selected intervals. Alternatively, test temperatures, information from electric logs and lithological descriptions of drill cuttings can be used to overcome these limitations. The present contribution introduces new heat flow determinations based on 63 exploration drillholes from the Norwegian North Sea, the Mid Norway Margin and the Barents Shelf. Our analyses are based on released DST temperatures, precise lithological descriptions of drill cuttings, previously measured rock matrix thermal conductivities and established porosity laws. For the sake of comparison, we carefully review previous heat flow studies carried out both onshore and offshore Norway. Our results suggest median heat flow values of 64 mW/m2, 65 mW/m2 and 72 mW/m2 for the North Sea, the Mid Norway Margin (mainly the Trøndelag Platform) and the SW Barents Shelf respectively. In detail, heat flow increases by ~ 10 mW/m2 from the southern Norwegian North Sea towards the Mid Norway Margin. This result appears to be in very good agreement with seismic tomographic studies suggesting northward thinning of the underlying mantle lithosphere. Our results together with published marine heat flow data from the Mid Norway Margin suggest a gradual decrease in heat flow levels from both the North Sea and the Trøndelag Platform towards the centres of the deep Møre and Vøring basins. This latter

  6. Modelisation of Circulation On The French Guiana Continental Shelf

    NASA Astrophysics Data System (ADS)

    Chevalier, C.; Dekeyser, I.; Ramamonjiarisoa, A.; Baklouti, M.; van Nieuwerberg, V.

    The continental shelf which extends more over than 1000 km to the north-west of the mouth of the Amazon river is an usual oceanographic environment : the entire area is influenced by fresh water flowing from the Amazon. The current on the shelf inter- acts with the strong, shallow Guiana Current along the outer shelf area. The prevailing trade winds across the area impose surface stresses. The tidal influence is also signif- icant with a diminishing amplitude from the Amazon to the north. This combination results in a persistent long-shore current flowing north-westward in the shallow wa- ter along the shore. In particular on French Guiana continental shelf, the combination of significant stratification, great coastal current just out of the shelf, influence of the wind and strong tidal component presents an interesting process for study. The purpose of this study is to look into the circulation that develops under these interacting forces. For that, we develop a numerical model of the circulation on the French Guiana shelf. Nowadays, in the bibliography, it seems to be the first numerical study on this area. This work is included in the Programme National dSEnvironnement Côtier (PNEC) in French Guiana. Simulations described the coastal currents, the salinity and temperature evolution on the shelf under the influence of rivers discharging in the shelf and the effect of north- eastward wind on the circulation. The current is parallel to the coast and the highest velocities are in the middle of the shelf, the maximum intensity is located at the surface and reached speed of 1m/s. The fresh water discharged by rivers extends alongshore near the coast, to about 30m-isobath, whereas the fresh water coming from the Ama- zon spreads out essentially in the middle of the shelf. The halocline is situated few meters (between 2 and 5 m) under the surface, with a lower salinity at the south-east boundary which is 20 and which is 25 at the north-west boundary, whereas, the

  7. U.S. Eastern Continental Shelf Carbon Cycling (USECoS): Modeling, Data Assimilation, and Analysis

    NASA Technical Reports Server (NTRS)

    Mannino, Antonio

    2008-01-01

    Although the oceans play a major role in the uptake of fossil fuel CO2 from the atmosphere, there is much debate about the contribution from continental shelves, since many key shelf fluxes are not yet well quantified: the exchange of carbon across the land-ocean and shelf-slope interfaces, air-sea exchange of CO2, burial, and biological processes including productivity. Our goal is to quantify these carbon fluxes along the eastern U.S. coast using models quantitatively verified by comparison to observations, and to establish a framework for predicting how these fluxes may be modified as a result of climate and land use change. Our research questions build on those addressed with previous NASA funding for the USECoS (U.S. Eastern Continental Shelf Carbon Cycling) project. We have developed a coupled biogeochemical ocean circulation model configured for this study region and have extensively evaluated this model with both in situ and remotely-sensed data. Results indicate that to further reduce uncertainties in the shelf component of the global carbon cycle, future efforts must be directed towards 1) increasing the resolution of the physical model via nesting and 2) making refinements to the biogeochemical model and quantitatively evaluating these via the assimilation of biogeochemical data (in situ and remotely-sensed). These model improvements are essential for better understanding and reducing estimates of uncertainties in current and future carbon transformations and cycling in continental shelf systems. Our approach and science questions are particularly germane to the carbon cycle science goals of the NASA Earth Science Research Program as well as the U.S. Climate Change Research Program and the North American Carbon Program. Our interdisciplinary research team consists of scientists who have expertise in the physics and biogeochemistry of the U.S. eastern continental shelf, remote-sensing data analysis and data assimilative numerical models.

  8. Comparison of marine productivity among Outer Continental Shelf planning areas

    SciTech Connect

    Darnell, R.M.

    1991-04-01

    Continental Shelf Associates was contracted to update and expand an earlier work on a comparison of primary productivity among Outer Continental Shelf (OCS) planning areas. The update consists of four general objectives. This report addresses the fourth objective, the potential to use measures of marine secondary productivity in determining relative rankings of the OCS planning area. Ideally, comparisons of secondary productivity among diverse geographic areas would take an ecosystem perspective. However, there is not enough ecosystem-level understanding to allow a comparison on that basis. The report focuses on individual species and group of species. Zooplankton and benthic communities represent major portions of the marine ecosystems and would be the preferred subjects for comparative studies. At this time comparisons of secondary productivity among planning areas would be difficult with existing databases. It is unlikely this situation will improve in the near future.

  9. Carbon Dynamics on the Louisiana Continental Shelf and Cross-Shelf Feeding of Hypoxia

    EPA Science Inventory

    Large-scale hypoxia regularly develops during the summer on the Louisiana continental shelf. Traditionally, hypoxia has been linked to the vast winter and spring nutrient inputs from the Mississippi River and its distributary, the Atchafalaya River. However, recent studies indica...

  10. Facies analysis of Nile delta continental shelf sediments off Egypt

    NASA Astrophysics Data System (ADS)

    Frihy, Omran E.; Gamai, Ibrahim H.

    This study evaluates the texture and coarse fraction composition of 108 bottom samples from the Nile delta continental shelf. In total 19 petrological variables were considered for each of the samples, and Q-mode factor analysis of the textural and mineralogical variables yielded 4 factors (facies groups): Facies I. Fine and very fine sands, light minerals, heavy minerals and 'glauconite', extending from the shoreline to the inner shelf and decreasing away from the shoreline. Facies II. Silty sand rich in biogenic components occupies the entire outer shelf and its contiguous lower terraces. Facies III. Mud (silt plus clay), mica and 'glauconite', covering the middle shelf and the upper terraces. Facies IV. Fine to coarse-grained sediments and 'glauconite', locally distributed along the coast off lake ldku, Burullus headland, and Damietta promontory and El Gamil. The configuration patterns of facies I (delta-front), facies III (prodelta) and facies IV (distributary mouth bar or progradational coastal sand) help identify delta lobes related to former distributary branches of the Nile river (Canopic, Saitic, Sebennitic, Atribic and Mendisian). The 4 facies-forming shelf sediments have resulted from sediment dynamics, sea-level fluctuation and differences in sediment input and provenance.

  11. The deglaciation history of the mid-Norwegian continental shelf

    NASA Astrophysics Data System (ADS)

    Haflidason, Haflidi; Bøyum, Eivind; Oline Hjelstuen, Berit

    2013-04-01

    The present knowledge on the last deglaciation of the mid-Norwegian continental shelf is still largely based on works from the late 1970's to early 1980's and improved by re-dating shell rich events using the AMS technology in the late 1990´s. These new dating results offered a new chronological framework for the two youngest till units identified in the outer shelf setting of the Mid-Norwegian shelf area using a regional grid of sparker lines. These till units were found to have been deposited around 15000 and 13500 14C BP. The results showed that the Mid-Norwegian shelf ice partly reached the shelf edge as late as ca. 13000 14C BP. Dating from the nearest coastal area show that most of the shelf area had been deglaciated in less than 1000 years. New high-resolution seismic technology, applying the TOPAS parametric echosounder system, the multibeam and the Olex data bathymetric data combined with new AMS dated gravity cores have in the recent year made it possible to approach the deglaciation history in a more detailed way than previously available. The results show that the last glacial maximum ice sheet retreated from the outer shelf area around 15200 14C. The ice sheet readvanced around 14500 14C and created a large end moraine complex and a new minor readvance is interpreted to have occurred around 13700 14C BP before a rapid retreat to the coastal areas during the Bølling period. The two dated ice sheet readvances have occurred within the period of the cold regional climatic event Heinrich 1.

  12. 76 FR 28178 - Renewable Energy Alternate Uses of Existing Facilities on the Outer Continental Shelf-Acquire a...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-05-16

    ... 9, 2008 (73 FR 39376). The North American Industry Classification System (NAICS) code for the... on February 16, 2011 (76 FR 8962), and received a total of 76 comments. The Offshore Wind Development... Energy Alternate Uses of Existing Facilities on the Outer Continental Shelf--Acquire a...

  13. Depositional history of Louisiana-Mississippi outer continental shelf

    USGS Publications Warehouse

    Kindinger, J.L.; Miller, R.J.; Stelting, C.E.

    1982-01-01

    A geological study was undertaken in 1981 in the Louisiana-Mississippi outer continental shelf for the Bureau of Land Management. The study included a high-resolution seismic reflection survey, surficial sediment sampling and surface current drifter sampling. Approximately 7100 sq km of the Louisiana-Mississippi shelf and upper slope were surveyed. The sea floor of the entire area is relatively smooth except for occasional areas of uplift produced by diapiric intrusion along the upper slope. Characteristics of the topography and subsurface shelf sediments are the result of depositional sequences due to delta outbuilding over transgressive sediments with intervening periods of erosion during low sea level stands. Little evidence of structural deformation such as faults, diapirs, and shallow gas is present on the shelf and only a few minor faults and scarps are found on the slope. Minisparker seismic records in combination with air gun (40 and 5 cu in) and 3.5-kHz subbottom profile records reveal that seven major stages of shelf development have occurred since the middle Pleistocene. The shelf development has been controlled by the rise and fall of sea level. These stages are defined by four major unconformities, several depositions of transgressive sediments, sequences of river channeling and progradational delta deposits. Surficial sediment sample and seismic records indicate tat the last major depositional event was the progradation of the St. Bernard Delta lobe. This delta lobe covered the northwestern and central regions. Surficial sediments in most of the study area are the product of the reworking of the San Bernard Delta lobe and previous progradations.

  14. Bryozoans from rio grande do sul continental shelf, southern Brazil.

    PubMed

    Ramalho, Laís V; Calliari, Lauro

    2015-01-01

    The continental shelf of Rio Grande do Sul (RS) is predominantly composed of unconsolidated sediments with a few hard substrates represented principally by beachrock. In this area there are elongate deposits of shell gravel material which are interpreted as indicators of the palaeo-shorelines. These Pleistocene deposits are overlapped by Holocene sediments (Recent), but are exposed during erosive events caused by extra-tropical cyclones, which provide the mixture of both sediments mainly during autumn and winter. The few studies on bryozoans made in this area previously recorded seven species, one fossil and the other six from Recent fluvial and marine environments. The aim of the present study was to describe the eight most abundant bryozoan species that occur in the inner RS shelf. Of these, four are new records for RS State (Arachnopusia aff. pusae, Hippomonavella brasiliensis, Turbicellepora pourtalesi, and Lifuella gorgonensis), and the other four are new to science (Chaperia taylori, Micropora nodimagna, Cellaria riograndensis, and Exochella moyani). PMID:25947873

  15. Southeastern U.S.A. Continental Shelf Respiratory Rates Revisited

    NASA Technical Reports Server (NTRS)

    Sheldon, Joan E.; Griffith, Peter C.; Peters Francesc; Sheldon, Wade M., Jr.; Blanton, Jackson O.; Amft, Julie; Pomeroy, Lawrence R.

    2010-01-01

    Respiratory rates on the U. S. southeastern continental shelf have been estimated several times by different investigators, most recently by Jiang et al. (Biogeochemistry 98:101-113, 2010) who report lower mean rates thanwere found in earlier work and attribute the differences to analytical error in all methods used in earlier studies. The differences are, instead, attributable to the differences in the geographical scope of the studies. The lower estimates of regional organic carbon flux of Jiang et al. (Biogeochemistry 98:101-113, 2010) are a consequence of their extrapolation of data from a small portion of the shelf to the entire South Atlantic Bight. This comment examines the methodologies used as well as the variability of respiratory rates in this region over space and time.

  16. Structure of the continental shelf west of San Francisco, California

    USGS Publications Warehouse

    Cooper, Alan K.

    1973-01-01

    The continental shelf west of San Francisco, California is divided into two structural provinces along the offshore extension of the Seal Cove fault, the Farallon and Golden Gate platforms. The Farallon platform lies west of the Seal Cove fault and is characterized by a thick sequence of Tertiary sediments with a maximum thickness of 3.5 km. These sediments are bounded at the edge of the continental shelf by a ridge of Cretaceous granitic rock which crops out at the Farallon Islands. The granitic basement is vertically displaced along the eastern flank of the granitic ridge and along two high angle reverse faults located near Point Reyes. The Point Reyes fault trends east-west and has possibly offset the granitic basement 1500 meters since late Pliocene time. Two northwest trending anticlines lie south of the Point Reyes fault. The eastern boundary of the Tertiary basin is delineated by a structural high composed of deformed basin sediments. This structural high is truncated at the Seal Cove fault. On the Golden Gate platform, the San Andreas fault zone is marked by a near surface graben, showing a maximum vertical displacement of 20 meters, and by a wider linear depression observed to a depth of 700 meters. The Pilarcitos fault continues offshore and joins the San Andreas fault south of Bolinas. The development of the present Tertiary basin under the continental shelf commenced in late Miocene time with. the initial uplift of the Farallon ridge and the compression of the eastern basin margin. Strike-slip faulting on the seal Cove fault in Pliocene time truncated middle Tertiary sediments at the fault and thus formed a distinct structural boundary between the Farallon and Golden Gate platforms. Surface extensional features observed within the San Andreas fault zone are suggestive of strike-slip faulting in late Tertiary time. The compressional high angle reverse faulting at Point Reyes occurred during the late Pliocene orogenic period of the California Coast Ranges.

  17. Surficial sediments on the western Canadian continental shelf

    NASA Astrophysics Data System (ADS)

    Bornhold, Brian D.; Barrie, J. Vaughn

    1991-08-01

    The active continental margin off western Canada is characterized in the south by convergence between the Explorer and Juan de Fuca Plates and the America Plate, and in the north by transform fault motion between the Pacific and America Plates along the Queen Charlotte Fault. Except in some of the deepest troughs and basins shelf sediments are dominated by immature lithic arenites reflecting this tectonic setting. The Vancouver Island shelf is from 5 to 75 km wide and displays complex topography on the inner shelf and a relatively featureless mid- and outer shelf. An exception is the area off southwestern Vancouver Island where large basins bounded by morainal deposits extend more than two-thirds of the distance across the shelf. The shelf edge varies from 180 to 225 m depth and is indented by numerous canyons. Nearshore sediments consist mainly of gravels and boulders and become finer offshore such that muds are slowly accumulating in depths greater than 100 m. Off northwestern Vancouver Island calcareous sediments are abundant with carbonate values often exceeding 75%. High wave and current energies and efficient sediment trapping in coastal fiords have resulted in low rates of accumulation. Olive, glauconitic, Holocene muds and muddy sands are generally less than 0.3 m thick and accumulate only on the outer shelf over an extensive stiff, gray, glaciomarine sandy mud. Queen Charlotte Sound exhibits three broad, shallow, glacially scoured troughs, filled mainly with clayey silts and fine sands and separated by sand and gravel covered banks. Hecate Strait, between the Queen Charlotte Islands and the mainland, consists of a prominent southward-opening trough along the east side of the Strait bounded by Dogfish and Laskeek Banks on the west adjacent to Graham and Moresby Islands, respectively. The trough below 200 m is filled by silts. The banks are covered by discontinuous sands and gravels of variable calcareous content. The bank edges often display megaripples and

  18. Continental shelf benthos off Otago Peninsula, New Zealand

    NASA Astrophysics Data System (ADS)

    Probert, P. Keith; Wilson, John B.

    1984-09-01

    Benthic macrofauna of the continental shelf off Otago Peninsula, south-eastern New Zealand (45°51'S, 170°52'E) was surveyed by dredge sampling during 1973-1975. Numerical classification (Canberra metric coefficient and flexible sorting) was used to produce site groups and species groups, and three major benthic communities were recognised: a shallow-water (14-25 m) fauna inhabiting well-sorted fine sand, a mid-shelf fauna (concentrated in the depth range 50-76 m) associated with sediments containing the greatest proportions of gravel and siltclay, and a predominantly sand-bottom fauna occurring mainly on the outer shelf (87-150 m). All station groups were dominated numerically by polychaetes (mean of 36·6-56% of individuals) with Mollusca (13·8-25%) or Crustacea (12·1-19·4%) the next most abundant group. The inshore sand fauna was the most distinct, characteristic elements being the trochid gastropod Antisolarium egenum, an amphipod of the genus Hippomedon and dense patches of the spionid polychaete Spiophanes bombyx. Diagnostic species of the mid-shelf mixed sediments were Lepidonotus jacksoni, Psammolyce antipoda, Lumbrineris brevicirra and Phyllamphicteis foliata (Polychaeta), Terenochiton otagoensis, Micrelenchus caelatus caelatus, Maoricolpus roseus roseus and Zegalerus tenuis (Mollusca), Ampelisca chiltoni (Amphipoda) and Amphipholis squamata (Ophiuroidea). Outer shelf sand stations were faunally less distinct, but among the more characteristic species were Euthalenessa fimbriata, Sigalion sp. and Euchone sp. (Polychaeta) and Gari stangeri (Bivalvia). Several abundant species were widely distributed among station groups, notably Nephtys macroura, Lumbrineris magalhaensis, Phyllochaetopterus socialis and Owenia fusiformis (Polychaeta) and Nucula nitidula and Tawera spissa (Bivalvia). Free-living lunulitiform Bryozoa of the genus Otionella were a characteristic component of inner and outer shelf sand faunas, and their inshore penetration probably marks

  19. Sources and Distribution of Organic Matter in Sediments of the Louisiana Continental Shelf

    EPA Science Inventory

    Both riverine and marine sources of organic matter (OM) contribute to sediment organic pools, and either source can contribute significantly to sediment accumulation, burial, and remineralization rates on river dominated continental shelf systems. For the Louisiana continental sh...

  20. 77 FR 10707 - Safety Zone; NOBLE DISCOVERER, Outer Continental Shelf Drillship, Chukchi and Beaufort Seas, Alaska

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-02-23

    ... SECURITY Coast Guard 33 CFR Part 147 RIN 1625-AA00 Safety Zone; NOBLE DISCOVERER, Outer Continental Shelf... prospects located in the Chukchi and Beaufort Seas Outer Continental Shelf, Alaska, from 12:01 a.m. on July... Federal Register (73 FR 3316). Public Meeting The Coast Guard does not plan to hold a public meeting....

  1. 78 FR 27427 - Outer Continental Shelf (OCS) Geological and Geophysical Exploration Activities in the Gulf of...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-05-10

    ... Bureau of Ocean Energy Management Outer Continental Shelf (OCS) Geological and Geophysical Exploration... ] Geological and Geophysical Exploration for Mineral Resources on the Gulf of Mexico Outer Continental Shelf... activities in GOM waters. It will also provide information for future decisions regarding Outer...

  2. 76 FR 29156 - Outer Continental Shelf Air Regulations Consistency Update for California

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-05-20

    ... AGENCY 40 CFR Part 55 Outer Continental Shelf Air Regulations Consistency Update for California AGENCY... Continental Shelf (``OCS'') Air Regulations proposed in the Federal Register on January 10, 2011. Requirements... Comment III. EPA Action IV. Statutory and Executive Order Reviews I. Background On January 10, 2011 (76...

  3. 75 FR 3387 - Outer Continental Shelf Air Regulations Consistency Update for Alaska

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-01-21

    ... AGENCY 40 CFR Part 55 Outer Continental Shelf Air Regulations Consistency Update for Alaska AGENCY... Continental Shelf (``OCS'') Air Regulations proposed in the Federal Register on March 3, 2009. Requirements... reader may refer to the Notice of Proposed Rulemaking, December 5, 1991 (56 FR 63774), and the...

  4. 77 FR 27480 - Outer Continental Shelf Scientific Committee; Announcement of Plenary Session

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-05-10

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF THE INTERIOR Bureau of Ocean Energy Management Outer Continental Shelf Scientific Committee; Announcement of Plenary...: The Outer Continental Shelf (OCS) Scientific Committee (SC) will meet at the Fess Parker's...

  5. 78 FR 64243 - Notice on Outer Continental Shelf Oil and Gas Lease Sales

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-10-28

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF THE INTERIOR Bureau of Ocean Energy Management Notice on Outer Continental Shelf Oil and Gas Lease Sales AGENCY... from bidding with any entity in any of the other following groups at Outer Continental Shelf oil...

  6. 78 FR 25100 - Outer Continental Shelf Scientific Committee; Announcement of Plenary Session

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-04-29

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF THE INTERIOR Bureau of Ocean Energy Management Outer Continental Shelf Scientific Committee; Announcement of Plenary...: The Outer Continental Shelf (OCS) Scientific Committee (SC) will meet at the Marriott Downtown...

  7. 75 FR 803 - Safety Zone; FRONTIER DISCOVERER, Outer Continental Shelf Drillship, Chukchi and Beaufort Sea...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-01-06

    ... the Chukchi and Beaufort Sea Outer Continental Shelf, Alaska, from 12:01 a.m. on July 1, 2010 through..., 2008 issue of the Federal Register (73 FR 3316). Public Meeting We do not now plan to hold a public... Continental Shelf, Alaska. Shell Exploration & Production Company has five proposed drill sites within...

  8. 75 FR 51968 - Outer Continental Shelf Air Regulations Consistency Update for Massachusetts

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-08-24

    ... From the Federal Register Online via the Government Publishing Office ENVIRONMENTAL PROTECTION AGENCY 40 CFR Part 55 Outer Continental Shelf Air Regulations Consistency Update for Massachusetts AGENCY... update to a portion of the Outer Continental Shelf (``OCS'') Air Regulations. Requirements applying...

  9. 76 FR 37274 - Outer Continental Shelf Air Regulations Consistency Update for Alaska

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-06-27

    ... AGENCY 40 CFR Part 55 Outer Continental Shelf Air Regulations Consistency Update for Alaska AGENCY... of the Outer Continental Shelf (``OCS'') Air Regulations proposed in the Federal Register on February... refer to the Notice of Proposed Rulemaking, December 5, 1991 (56 FR 63774), and the preamble to...

  10. 76 FR 1389 - Outer Continental Shelf Air Regulations Consistency Update for California

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-01-10

    ... AGENCY 40 CFR Part 55 Outer Continental Shelf Air Regulations Consistency Update for California AGENCY... of the Outer Continental Shelf (``OCS'') Air Regulations. Requirements applying to OCS sources... FR 63774), and the preamble to the final rule promulgated September 4, 1992 (57 FR 40792) for...

  11. 76 FR 15898 - Outer Continental Shelf Air Regulations; Consistency Update for California

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-03-22

    ... AGENCY 40 CFR Part 55 Outer Continental Shelf Air Regulations; Consistency Update for California AGENCY... of the Outer Continental Shelf (``OCS'') Air Regulations. Requirements applying to OCS sources... onshore requirements. \\1\\ See Notice of Proposed Rulemaking, December 5, 1991 (56 FR 63774), and...

  12. 76 FR 7518 - Outer Continental Shelf Air Regulations Consistency Update for Alaska

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-02-10

    ... AGENCY 40 CFR Part 55 Outer Continental Shelf Air Regulations Consistency Update for Alaska AGENCY... of the Outer Continental Shelf (``OCS'') Air Regulations. Requirements applying to OCS sources... 5, 1991 (56 FR 63774), and the preamble to the final rule promulgated September 4, 1992 (57 FR...

  13. 75 FR 9780 - Technical Amendment to the Outer Continental Shelf Air Regulations Consistency Update; Correction

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-03-04

    ... AGENCY 40 CFR Part 55 Technical Amendment to the Outer Continental Shelf Air Regulations Consistency... Outer Continental Shelf Air Regulations for Alaska. DATES: Effective on March 22, 2010. FOR FURTHER... Information This Notice is to provide a technical correction to the final regulation published at 75 FR...

  14. 75 FR 3392 - Outer Continental Shelf Air Regulations Consistency Update for Alaska

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-01-21

    ... AGENCY 40 CFR Part 55 Outer Continental Shelf Air Regulations Consistency Update for Alaska AGENCY... 50.410. Requirements applying to Outer Continental Shelf (``OCS'') sources located within 25 miles of... FR 63774), and the preamble to the final rule promulgated September 4, 1992 (57 FR 40792) for...

  15. 78 FR 33859 - Outer Continental Shelf (OCS) Geological and Geophysical Exploration Activities in the Gulf of...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-06-05

    ... Bureau of Ocean Energy Management Outer Continental Shelf (OCS) Geological and Geophysical Exploration.... SUMMARY: On May 10, 2013, BOEM published a document in the Federal Register (78 FR 27427) entitled ``Outer Continental Shelf Geological and Geophysical Exploration Activities in the Gulf of Mexico.'' This...

  16. 76 FR 28449 - Notice on Outer Continental Shelf Oil and Gas Lease Sales

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-05-17

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF THE INTERIOR Bureau of Ocean Energy Management, Regulation and Enforcement (BOEMRE) Notice on Outer Continental Shelf... with any entity in any other of the following groups at Outer Continental Shelf oil and gas lease...

  17. 76 FR 43185 - Outer Continental Shelf Air Regulations Consistency Update for Virginia

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-07-20

    ... AGENCY 40 CFR Part 55 Outer Continental Shelf Air Regulations Consistency Update for Virginia AGENCY... approve an update to a portion of the Outer Continental Shelf (OCS) Air Regulations. Requirements applying...'' subject to review by the Office of Management and Budget under Executive Order 12866 (58 FR 51735,...

  18. 76 FR 67759 - Notice on Outer Continental Shelf Oil and Gas Lease Sales

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-11-02

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF THE INTERIOR Bureau of Ocean Energy Management Notice on Outer Continental Shelf Oil and Gas Lease Sales AGENCY... from bidding with any entity in any other of the following groups at Outer Continental Shelf oil...

  19. 78 FR 27430 - Notice on Outer Continental Shelf Oil and Gas Lease Sales

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-05-10

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF THE INTERIOR Bureau of Ocean Energy Management Notice on Outer Continental Shelf Oil and Gas Lease Sales AGENCY... from bidding with any entity in any of the other following groups at Outer Continental Shelf oil...

  20. 76 FR 4129 - Notice on Outer Continental Shelf Oil and Gas Lease Sales

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-01-24

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF THE INTERIOR Bureau of Ocean Energy Management, Regulation and Enforcement Notice on Outer Continental Shelf Oil and... any entity in any other of the following groups at Outer Continental Shelf oil and gas lease sales...

  1. 77 FR 24980 - Notice on Outer Continental Shelf Oil and Gas Lease Sales

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-04-26

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF THE INTERIOR Bureau of Ocean Energy Management Notice on Outer Continental Shelf Oil and Gas Lease Sales AGENCY... from bidding with any entity in any other of the following groups at Outer Continental Shelf oil...

  2. 75 FR 24966 - Notice on Outer Continental Shelf Oil and Gas Lease Sales

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-05-06

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF THE INTERIOR Minerals Management Service Notice on Outer Continental Shelf Oil and Gas Lease Sales AGENCY: Minerals... in any other of the following groups at Outer Continental Shelf oil and gas lease sales to be...

  3. 77 FR 64826 - Notice on Outer Continental Shelf Oil and Gas Lease Sales

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-10-23

    ... From the Federal Register Online via the Government Publishing Office ] DEPARTMENT OF THE INTERIOR Bureau of Ocean Energy Management (BOEM) Notice on Outer Continental Shelf Oil and Gas Lease Sales AGENCY... with any entity in any of the other following groups at Outer Continental Shelf oil and gas lease...

  4. Carbonate sediment production in the equatorial continental shelf of South America: Quantifying Halimeda incrassata (Chlorophyta) contributions

    NASA Astrophysics Data System (ADS)

    Carneiro, Pedro Bastos de Macêdo; Morais, Jader Onofre de

    2016-12-01

    The middle and outer continental shelves of eastern equatorial South America (ESA) are characterized by intense production of carbonate sediments. Qualitative analyses of sediment deposits suggest that the calcareous green alga Halimeda incrassata is among the top CaCO3 producers. Nevertheless, no study so far has quantified its real contributions. To better understand the sediment dynamic in this area, we measured biomass, growth rates and calcium carbonate production by this alga. The species exhibited high growth rates (3.38 segments.individual-1.day-1), coverage (174 individuals.m-2) and biomass (214.02 g.m-2). Substitution of segments may allow a sedimentation rate of 1.53 mm.yr-1 and a complete turnover of the population every 60.2 days. The rapid growth indicates that this alga can produce as much CaCO3 (1.19 kg CaCO3.m-2.year-1) as other tropical organisms, such as corals and rhodoliths. In a conservative estimate, 773.500 tonnes of CaCO3 are produced per year in a 5000 km2 area off the northern coast of Brazil. Sedimentation rate seems to be higher than that promoted by continental inputs in middle and outer continental shelf. On the other hand, population turnover is twice as slow as in other H. incrassata assemblages, suggesting that South American populations are sensible to physical disturbances. New studies are necessary to accurately estimate H. incrassata coverage along the Brazilian coast and to integrate data on other CaCO3 producers, such as foraminifera and coralline algae. This would allow a better understanding of the role of South American continental shelf on the global carbon budget. Furthermore, analysis on the health of these organisms is urgent, since a decline in their populations could negatively affect ecosystems functioning and services.

  5. Potential alternative energy technologies on the Outer Continental Shelf.

    SciTech Connect

    Elcock, D.; Environmental Assessment

    2007-04-20

    This technical memorandum (TM) describes the technology requirements for three alternative energy technologies for which pilot and/or commercial projects on the U.S. Outer Continental Shelf (OCS) are likely to be proposed within the next five to seven years. For each of the alternative technologies--wind, wave, and ocean current--the TM first presents an overview. After each technology-specific overview, it describes the technology requirements for four development phases: site monitoring and testing, construction, operation, and decommissioning. For each phase, the report covers the following topics (where data are available): facility description, electricity generated, ocean area (surface and bottom) occupied, resource requirements, emissions and noise sources, hazardous materials stored or used, transportation requirements, and accident potential. Where appropriate, the TM distinguishes between pilot-scale (or demonstration-scale) facilities and commercial-scale facilities.

  6. Habitat Specialization in Tropical Continental Shelf Demersal Fish Assemblages

    PubMed Central

    Fitzpatrick, Ben M.; Harvey, Euan S.; Heyward, Andrew J.; Twiggs, Emily J.; Colquhoun, Jamie

    2012-01-01

    The implications of shallow water impacts such as fishing and climate change on fish assemblages are generally considered in isolation from the distribution and abundance of these fish assemblages in adjacent deeper waters. We investigate the abundance and length of demersal fish assemblages across a section of tropical continental shelf at Ningaloo Reef, Western Australia, to identify fish and fish habitat relationships across steep gradients in depth and in different benthic habitat types. The assemblage composition of demersal fish were assessed from baited remote underwater stereo-video samples (n = 304) collected from 16 depth and habitat combinations. Samples were collected across a depth range poorly represented in the literature from the fringing reef lagoon (1–10 m depth), down the fore reef slope to the reef base (10–30 m depth) then across the adjacent continental shelf (30–110 m depth). Multivariate analyses showed that there were distinctive fish assemblages and different sized fish were associated with each habitat/depth category. Species richness, MaxN and diversity declined with depth, while average length and trophic level increased. The assemblage structure, diversity, size and trophic structure of demersal fishes changes from shallow inshore habitats to deeper water habitats. More habitat specialists (unique species per habitat/depth category) were associated with the reef slope and reef base than other habitats, but offshore sponge-dominated habitats and inshore coral-dominated reef also supported unique species. This suggests that marine protected areas in shallow coral-dominated reef habitats may not adequately protect those species whose depth distribution extends beyond shallow habitats, or other significant elements of demersal fish biodiversity. The ontogenetic habitat partitioning which is characteristic of many species, suggests that to maintain entire species life histories it is necessary to protect corridors of connected

  7. Cathodoluminescent bimineralic ooids from Pleistocene of Florida continental shelf

    SciTech Connect

    Major, R.P.; Halley, R.B.; Lukas, K.J.

    1987-05-01

    A bored and encrusted late Pleistocene ooid grainstone was recovered from the sea floor at a depth of approximately 40 m on the continental shelf of eastern Florida. Ooid cortices are dominantly bimineralic, consisting generally of inner layers of radial magnesian calcite and outer layers of tangential aragonite. The transition from radial to tangential cortex layers occurs at an approximate diameter of 0.30 to 0.35 mm. Ooid nuclei are predominantly rounded cryptocrystalline grains, although quartz grains and a variety of skeletal grains also occur as nuclei. Ooids were partially cemented by blocky calcite, followed by partial infilling of interparticle porosity by micrite and subsequently by sparse acicular cement. The radial cortex layers and some ooid nuclei are brightly cathodoluminescent, whereas the tangential cortex layers, micrite matrix, acicular cement, and the bulk of blocky calcite cement are nonluminescent. Some blocky calcite cement has a thin outer cathodoluminescent zone. Electron microprobe analyses indicate that radial layers contain approximately 10 mole % MgCO/sub 3/ and tangential layers generally contain 10,000 to 11,000 ppm strontium. The manganese content of radial layers ranges as high as 250 ppm, whereas the manganese content of tangential layers is generally below the detection limit of approximately 100 ppm. Iron content varies over a wide range. Scanning electron microscope analysis indicates no microdolomites. They assume manganese is the principal cathodoluminescent activator. Although there is some uncertainty concerning the partition coefficient for manganese into magnesian calcite and the influence of kinetic effects at varying rates of precipitation is poorly understood, they favor the interpretation that these cathodoluminescent magnesian calcite cortex layers have undergone diagenetic alteration in sea water of the Florida continental shelf.

  8. Analysis of the petroleum resources of the Norwegian Continental Shelf

    SciTech Connect

    Flertoft, I.P.; Kvadsheim, E.; Kalheim, J.E.

    1995-08-01

    The 1995 analysis of the petroleum resources of Norway is based on a play analysis. The input to the 1995 analysis is updated and refined compared with the analysis of 1993. The analysis makes a major distinction between unconfirmed play models and plays confirmed by discoveries. The unconfirmed plays have a higher risk and a greater range of uncertainty in the resource estimates compared to the confirmed plays. The effect of the unconfirmed plays on the estimates within different exploration areas is discussed. The unconfirmed play models are an important aspect of the exploration in the new exploration areas north of 62{degrees}N. The total estimate for the Norwegian Shelf is well within the estimate given in the 1993 analysis, but there are some adjustments in the relative importance of the different exploration provinces. Much emphasis is placed on incorporating historical exploration data and statistics to calibrate the play models. This includes rate of success and field size distributions of the individual play models and exploration provinces. Major confirmed plays in the North Sea have a rate of success of about 30% and show a good fit to a log normal field size distribution. Based on the log normal distribution it is possible to give prognosis for the size distribution of the undiscovered accumulation. This has made it possible to work out an economic analysis of the profitability of future exploration on the Norwegian Continental Shelf.

  9. Anomalous topography on the continental shelf around Hudson Canyon

    USGS Publications Warehouse

    Knebel, H. J.

    1979-01-01

    Recent seismic-reflection data show that the topography on the Continental Shelf around Hudson Canyon is composed of a series of depressions having variable spacings (< 100 m to 2 km), depths (1-10 m), outlines, and bottom configurations that give the sea floor an anomalous "jagged" appearance in profile. The acoustic and sedimentary characteristics, the proximity to relict shores, and the areal distribution indicate that this rough topography is an erosional surface formed on Upper Pleistocene silty sands about 13,000 to 15,000 years ago by processes related to Hudson Canyon. The pronounced southward extension of the surface, in particular, may reflect a former increase in the longshore-current erosion capacity caused by the loss of sediments over the canyon. Modern erosion or nondeposition of sediments has prevented the ubiquitous sand sheet on the Middle Atlantic shelf from covering the surface. The "anomalous" topography may, in fact, be characteristic of areas near other submarine canyons that interrupt or have interrupted the longshore drift of sediments. ?? 1979.

  10. Inversion of IceBridge gravity data for continental shelf bathymetry beneath the Larsen ice shelf (Invited)

    NASA Astrophysics Data System (ADS)

    Cochran, J. R.; Bell, R. E.; Frearson, N.; Elieff, S.

    2010-12-01

    Accurate bathymetry beneath large ice shelves is crucial for developing models of the ocean circulation in the large sub-ice cavities and for effectively deploying moorings to monitor changing conditions. Improved models and observations should improve our understanding of how these large ice shelves collapse. A grid of free-air gravity data collected during the IceBridge 2009 Antarctic campaign over the floating Larsen C ice shelf was utilized to investigate the bathymetry of the underlying continental shelf. Data were collected with a Sander AIRGrav system mounted in a NASA DC-8 aircraft and flown at an altitude of about 500 m above the ice surface. Airborne data were augmented by upward continued marine gravity data from the former Larsen B ice shelf to provide control in an area where the bathymetry is known. Independent control on the geologic structures of the continental shelf was used to constrain the bathymetric inversion. The bathymetry determined by inverting the gravity data generally agrees with the shipboard bathymetry to within ±30 m and with a BAS seismic refraction line at 67°30’S on the ice shelf to 24 m. Simultaneously collected laser altimetry and radar data allow the geometry of the water-filled cavity to be investigated. Depths on the continental shelf beneath the ice shelf estimated from the inversion average about 450-600 m, but vary greatly from less than 300 m to greater than 1000 m. Distinctive localized overdeepenings, 20-30 km wide and reaching 900-1000 m deep are located in the inlets where three to five glaciers converge. Submarine valleys extending seaward from the overdeepened areas coalesce into three broad channels that extend to the seaward limit of the ice shelf and appear to extend to the edge of the continental shelf. The channels generally are at a depth of 550-700 m although the southernmost mapped channel deepens to over 1000 m near the edge of the ice shelf just south of 68°S. These newly imaged channels provide a

  11. 77 FR 74204 - Commercial Leasing for Wind Power on the Outer Continental Shelf Offshore North Carolina-Call for...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-12-13

    ... Bureau of Ocean Energy Management Commercial Leasing for Wind Power on the Outer Continental Shelf... Power on the Outer Continental Shelf, Offshore North Carolina. SUMMARY: BOEM invites the submission of... project on the Outer Continental Shelf (OCS) offshore North Carolina, and to develop the project...

  12. 77 FR 29682 - Gulf of Mexico, Outer Continental Shelf, Central Planning Area, Oil and Gas Lease Sale 216/222

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-05-18

    ... Bureau of Ocean Energy Management Gulf of Mexico, Outer Continental Shelf, Central Planning Area, Oil and...) for Gulf of Mexico (GOM), Outer Continental Shelf (OCS) Oil and Gas Lease Sale: 2012 Central Planning... of the continental shelf boundary between the United States and Mexico. The CPA lease sale...

  13. 77 FR 38718 - Safety Zone; NOBLE DISCOVERER, Outer Continental Shelf Drillship, Chukchi and/or Beaufort Seas, AK

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-06-29

    ... SECURITY Coast Guard 33 CFR Part 147 RIN 1625-AA00 Safety Zone; NOBLE DISCOVERER, Outer Continental Shelf... Seas Outer Continental Shelf, Alaska, on or about July 1, 2012 through November 30, 2012. See TABLE 1...; NOBLE DISCOVERER, Outer Continental Shelf Drillship, Chukchi and Beaufort Seas, Alaska'' in the...

  14. 76 FR 38294 - Oil and Gas and Sulphur Operations in the Outer Continental Shelf-Civil Penalties

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-06-30

    ... and Gas and Sulphur Operations in the Outer Continental Shelf--Civil Penalties AGENCY: Bureau of Ocean... Continental Shelf Lands Act (OCSLA) requires the Bureau of Ocean Energy Management, Regulation and Enforcement...@boemre.gov . SUPPLEMENTARY INFORMATION: Background The goal of BOEMRE's Outer Continental Shelf...

  15. 75 FR 19880 - Safety Zone; BW PIONEER at Walker Ridge 249, Outer Continental Shelf FPSO, Gulf of Mexico

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-04-16

    ... PIONEER at Walker Ridge 249, Outer Continental Shelf FPSO, Gulf of Mexico in the Federal Register (74 FR... Continental Shelf FPSO, Gulf of Mexico AGENCY: Coast Guard, DHS. ACTION: Final rule. SUMMARY: The Coast Guard... (FPSO) system, at Walker Ridge 249 in the Outer Continental Shelf. The purpose of the safety zone is...

  16. 77 FR 5529 - Commercial Lease of Submerged Lands for Renewable Energy Development on the Outer Continental Shelf

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-02-03

    ... the Outer Continental Shelf AGENCY: Bureau of Ocean Energy Management, Interior. ACTION: Notice... energy leases on the Outer Continental Shelf (OCS). In the preamble to the April 29, 2009, Final Rule, ``Renewable Energy and Alternate Uses of Existing Facilities on the Outer Continental Shelf,'' BOEM...

  17. 75 FR 76632 - Oil and Gas and Sulphur Operations in the Outer Continental Shelf-Increased Safety Measures for...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-12-09

    ... and Sulphur Operations in the Outer Continental Shelf--Increased Safety Measures for Energy Development on the Outer Continental Shelf; Correction AGENCY: Bureau of Ocean Energy Management, Regulation... oil and gas exploration and development on the Outer Continental Shelf. This document contains...

  18. 76 FR 55090 - Commercial Lease of Submerged Lands for Renewable Energy Development on the Outer Continental Shelf

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-09-06

    ... Renewable Energy Development on the Outer Continental Shelf AGENCY: Bureau of Ocean Energy Management... will use Form 0008 to issue commercial renewable energy leases on the Outer Continental Shelf. In the... the Outer Continental Shelf,'' BOEMRE stated that ``we intend to develop a model lease form through...

  19. Estimating rocky seafloor extent on the Southern California continental shelf

    USGS Publications Warehouse

    Cochrane, G.R.; Greene, H. Gary

    2009-01-01

    High-resolution sonar data are necessary to map bottom substrate for habitat studies but are lacking over much of the continental shelf. With such data, areas covered by sediment can be distinguished from bedrock areas with an accuracy of ??90%. Without these data, the extent of sediment as thick as 10 m cannot be resolved, and estimates of the extent of rocky seafloor are exaggerated. A study area north of Anacapa Island in Southern California interpreted as a large rocky area after mapping with low-resolution seismic systems was found to have exposed rocky bottom in only 10% of the area when mapped with high-resolution, side-scan sonar. The area of rock was estimated using video-supervised, sonar-image classification of textural derivatives of the data calculated from gray-level co-occurrence matrices. The classification of soft bottom was found to be ??90% accurate using an independent data set, derived from seafloor sampling records. Two general types of rock exposure are observed-sparse linear outcrops of layered sedimentary rocks and more massive, rounded outcrop areas of volcanic rocks. The percentage of exposed rock in volcanic areas exceeded that in sedimentary rock areas by a factor of 5 in the study area north of Anacapa Island. South of Point Arguello, 80% of the shelf seafloor is underlain by sedimentary rock units. The percentage of area that is exposed, rocky-reef habitat may be greater in other areas of coastal seafloor if the bedrock is predominantly volcanic. ?? 2009 The Geological Society of America.

  20. On instability and mixing on the UK Continental Shelf

    NASA Astrophysics Data System (ADS)

    Liu, Zhiyu

    2016-06-01

    The stability of stratified flows at locations in the Clyde, Irish and Celtic Seas on the UK Continental Shelf is examined. Flows are averaged over periods of 12-30 min in each hour, corresponding to the times taken to obtain reliable estimates of the rate of dissipation of turbulent kinetic energy per unit mass, ε. The Taylor-Goldstein equation is solved to find the maximum growth rate of small disturbances to these averaged flows, and the critical gradient Richardson number, Ric. The proportion of unstable periods where the minimum gradient Richardson number, Rimin, is less than Ric is about 35%. Cases are found in which Ric < 0.25; 37% of the flows with Rimin < 0.25 are stable, and Ric < 0.24 in 68% of the periods where Rimin < 0.25. Marginal conditions with 0.8 < Rimin/Ric < 1.2 occur in 30% of the periods examined. The mean dissipation rate at the level where the fastest growing disturbance has its maximum amplitude is examined to assess whether the turbulence there is isotropic and how it relates to the wave-turbulence boundary. It is concluded that there is a background level of dissipation that is augmented by instability; instability of the averaged flow does not account for all the turbulence observed in mid-water. The effects of a horizontal separation of the measurements of shear and buoyancy are considered. The available data do not support the hypothesis that the turbulent flows observed on the UK shelf adjust rapidly to conditions that are close to being marginal, or that flows in a particular location and period of time in one sea have stability characteristics that are very similar to those in another.

  1. Export and Cycling of Continental Shelf Carbon: A Modeling Study

    NASA Astrophysics Data System (ADS)

    Siedlecki, S.; Archer, D.; Mahadevan, A.

    2004-12-01

    Continental margins play a significant role in the production and burial of organic carbon in the ocean, but these areas are poorly resolved in global circulation models. In this study, a high-resolution three-dimensional, nonhydrostatic idealized coastal model of the eastern United States after Mahadevan and Archer, 2000, 1998, was modified to simulate organic carbon production and export off the shelf. The model assumes a periodic north and south boundary, solid offshore and bottom boundaries, and a shelf-break density front determined by bathymetry. The model uses a free surface and a sigma grid in the vertical. We are in the process of formulating a carbon and nutrient component for this model. The model is initialized with a vertical nutrient profile taken from the open Atlantic Ocean. Mesoscale wind-driven circulation and vertical diffusion bring nutrients to the euphotic zone. Primary production is based on light availability and nutrient concentration. The particles advect with the flow and sink with a specified velocity. Remineralization is first-order in carbon concentration, and produces ammonia. Ammonia is slowly reoxidized to nitrate in subsurface waters, and used for recycled production in the euphotic zone. We are searching for a model of the production, sinking, and interconversion of multiple types of particles, which predicts the observed trends in f-ratio from coastal to pelagic ecosystems. The model is sensitive to sinking velocity, remineralization rate, vertical diffusivity, the uptake rate of nitrate, the uptake rate of ammonia, and the oxidation rate of ammonia to nitrate. Using the steady state solution of the one-dimensional model to initialize the three-dimensional model, we study the effect of vertical and horizontal advection and three-dimensional oceanographic processes on the distribution and export of carbon from the coastal system. We will compare the sensitivities of a box-budget, a one-dimensional diffusional, and the full 3-D

  2. Observational evidence for tidal straining over a sloping continental shelf

    NASA Astrophysics Data System (ADS)

    Endoh, Takahiro; Yoshikawa, Yutaka; Matsuno, Takeshi; Wakata, Yoshinobu; Lee, Keun-Jong; Umlauf, Lars

    2016-04-01

    Straining of a horizontal density gradient by tidal currents acts to periodically produce and destroy near-bottom stratification, which has been shown to modulate turbulence in the bottom boundary layer (BBL). Previous observations of such periodic variations have been limited to the coastal ocean and estuaries, where horizontal density gradients are maintained by river runoff or differential heating. In the present study, we show evidence for the existence of tidal straining over the continental shelf, outside any regions of freshwater influence, where horizontal density gradients are likely to result from the projection of the interior vertical stratification onto sloping topography. Based on microstructure data obtained in the East China Sea, we demonstrate that the tidal current shear interacting with the cross-isobath density gradient results in semidiurnal switching between unstable and stable stratification in the lower part of the BBL. The cycle of turbulent dissipation is quarter-diurnal, corresponding to the semidiurnal variation of tidal current shear. In addition, a noticeable diurnal modulation in stratification as well as a significant diurnal cycle of turbulent dissipation are observed in the upper part of the BBL, where the time evolution of stratification is dominated by tidal advection, rather than tidal straining.

  3. Trophic interactions within the Ross Sea continental shelf ecosystem

    PubMed Central

    Smith, Walker O; Ainley, David G; Cattaneo-Vietti, Riccardo

    2006-01-01

    The continental shelf of the Ross Sea is one of the Antarctic's most intensively studied regions. We review the available data on the region's physical characteristics (currents and ice concentrations) and their spatial variations, as well as components of the neritic food web, including lower and middle levels (phytoplankton, zooplankton, krill, fishes), the upper trophic levels (seals, penguins, pelagic birds, whales) and benthic fauna. A hypothetical food web is presented. Biotic interactions, such as the role of Euphausia crystallorophias and Pleuragramma antarcticum as grazers of lower levels and food for higher trophic levels, are suggested as being critical. The neritic food web contrasts dramatically with others in the Antarctic that appear to be structured around the keystone species Euphausia superba. Similarly, we suggest that benthic–pelagic coupling is stronger in the Ross Sea than in most other Antarctic regions. We also highlight many of the unknowns within the food web, and discuss the impacts of a changing Ross Sea habitat on the ecosystem. PMID:17405209

  4. 77 FR 19321 - Geological and Geophysical Exploration on the Atlantic Outer Continental Shelf (OCS)

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-03-30

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF THE INTERIOR Bureau of Ocean Energy Management Geological and Geophysical Exploration on the Atlantic Outer Continental Shelf (OCS) AGENCY: Bureau of Ocean Energy Management (BOEM), Interior. ACTION: Notice...

  5. 76 FR 23331 - Outer Continental Shelf (OCS) Scientific Committee (SC); Announcement of Plenary Session

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-04-26

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF THE INTERIOR Bureau of Ocean Energy Management, Regulation and Enforcement Outer Continental Shelf (OCS) Scientific Committee (SC); Announcement of Plenary Session AGENCY: Bureau of Ocean Energy Management, Regulation...

  6. 77 FR 4056 - Outer Continental Shelf (OCS) Scientific Committee (SC); Announcement of Plenary Session

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-01-26

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF THE INTERIOR Bureau of Ocean Energy Management Outer Continental Shelf (OCS) Scientific Committee (SC); Announcement of Plenary Session AGENCY: Bureau of Ocean Energy Management (BOEM), Interior. ACTION: Notice...

  7. Phytoplankton Community Structure, Biomass and Diversity on the Louisiana Continental Shelf

    EPA Science Inventory

    Phytoplankton communities on the Louisiana continental shelf (LCS) respond to nutrient loading from the Mississippi and Atchafalaya River Basin (MARB). Enhanced phytoplankton biomass is a source of organic matter contributing to the development of seasonal hypoxia. Samples were ...

  8. Geology of continental shelf, Onslow Bay, North Carolina, as revealed by submarine outcrops ( USA).

    USGS Publications Warehouse

    Blackwelder, B. W.; Macintyre, Ian G.; Pilkey, O.H.

    1982-01-01

    Lithologic and stratigraphic data from rocks dredged from the continental shelf off Onslow Bay, North Carolina, provide surface control for seismic studies of the southeastern United States continental margin and help to explain the distribution of potentially economic phosphate-rich sediments on this shelf. Outcropping Miocene rocks in this area indicate that the region has long been a positive geologic feature and has received relatively little Pliocene and Pleistocene sedimentation. -from Authors

  9. Problem on the United States Continental Shelf - measuring the environmental {open_quotes}effectiveness{close_quotes} of the Outer Continental Shelf Act (OCSA)

    SciTech Connect

    Dubner, B.H.

    1994-12-31

    This article reviews the interplay of environmental standard with oil and gas leasing on the Outer Continental Shelf (OSC) in order to determine if the marine environment is really protected by the interplay of domestic legislation. The 1982 LOS treaty leaves environmental protection to State (domestic) regulation. There is no customary law regarding this type of domestic shelf regulation. The main problem is measuring the {open_quotes}effectiveness{close_quotes} of our domestic shelf legislation. For example, do we simply review effectiveness in terms of controlling operational damage or in terms of environmental injury caused by catastrophic accidents?

  10. Drowned forests and archaeology on the continental shelf of British Columbia, Canada

    NASA Astrophysics Data System (ADS)

    Fedje, Daryl W.; Josenhans, Heiner

    2000-02-01

    We have used high-resolution digital terrain imaging and sea-floor sampling to reveal drowned late glacial to early postglacial terrestrial landscapes at water depths as great as 150 m. In situ tree stumps and shellfish-rich paleobeaches are present on these drowned landscapes. A stone tool encrusted with barnacles and bryozoa was recovered from a drowned delta flood plain now 53 m below mean sea level. This is the first tangible evidence that the formerly subaerial broad banks of the western North American Continental Shelf may have been occupied by humans in earliest Holocene and possibly late-glacial time. Analyses (14C) of the drowned terrestrial and intertidal deposits were used to refine the local sea-level curve, which shows very rapid change within this glacio-isostatically dynamic region.

  11. Seafloor Rocks and Sediments of the Continental Shelf From Monterey Bay to Point Sur, California

    USGS Publications Warehouse

    Eittreim, Stephen L.; Anima, Roberto J.; Stevenson, Andrew J.; Wong, Florence L.

    2000-01-01

    Introduction Acoustic swath mapping of the greater Monterey Bay area continental shelf from Point Ano Nuevo to Point Sur reveals complex patterns of rock outcrops on the shelf, and coarse sand bodies that occur in distinct depressions on the inner and mid-shelves. This publication portrays the seafloor components in a 36- by 48-inch map sheet at 1:100,000 scale.

  12. Some Cenozoic hydrocarbon basins on the continental shelf of Vietnam

    SciTech Connect

    Dien, P.T.

    1994-07-01

    The formation of the East Vietnam Sea basins was related to different geodynamic processes. The pre-Oligocene basement consists of igneous, metamorphic, and metasediment complexes. The Cretaceous-Eocene basement formations are formed by convergence of continents after destruction of the Tethys Ocean. Many Jurassic-Eocene fractured magmatic highs of the Cuulong basin basement constitute important reservoirs that are producing good crude oil. The Paleocene-Eocene formations are characterized by intramountain metamolasses, sometimes interbedded volcanic rocks. Interior structures of the Tertiary basins connect with rifted branches of the widened East Vietnam Sea. Bacbo (Song Hong) basin is predominated by alluvial-rhythmic clastics in high-constructive deltas, which developed on the rifting and sagging structures of the continental branch. Petroleum plays are constituted from Type III source rocks, clastic reservoirs, and local caprocks. Cuulong basin represents sagging structures and is predominated by fine clastics, with tidal-lagoonal fine sandstone and shalestone in high-destructive deltas that are rich in Type II source rocks. The association of the pre-Cenozoic fractured basement reservoirs and the Oligocene-Miocene clastic reservoir sequences with the Oligocene source rocks and the good caprocks is frequently met in petroleum plays of this basin. Nan Conson basin was formed from complicated structures that are related to spreading of the oceanic branch. This basin is characterized by Oligocene epicontinental fine clastics and Miocene marine carbonates that are rich in Types I, II, and III organic matter. There are both pre-Cenozoic fractured basement reservoirs, Miocene buildup carbonate reservoir rocks and Oligocene-Miocene clastic reservoir sequences, in this basin. Pliocene-Quaternary sediments are sand and mud carbonates in the shelf facies of the East Vietnam Sea back-arc basin. Their great thickness provides good conditions for maturation and trapping.

  13. Manganese, iron, and sulfur cycling in Louisiana continental shelf sediments

    NASA Astrophysics Data System (ADS)

    Devereux, Richard; Lehrter, John C.; Beddick, David L.; Yates, Diane F.; Jarvis, Brandon M.

    2015-05-01

    Sulfate reduction is considered the primary pathway for organic carbon remineralization on the northern Gulf of Mexico Louisiana continental shelf (LCS) where bottom waters are seasonally hypoxic, yet limited information is available on the importance of iron and manganese cycling in the region. Sedimentary manganese, iron, and sulfur cycling were investigated on the LCS using a combined chemical analysis and sediment diagenesis modeling approach. Three stations situated 320 km across the LCS along the 20 m isobath were sampled up to five times between the spring of 2006 and summer of 2007. Bottom water oxygen levels at the stations ranged from 203 mmol m-3 in spring to 2.5 mmol m-3 in summer. Porewater Mn and Fe2+ concentrations (up to 275 and 300 μmol L-1, respectively), sulfate reduction rates (1.0-8.4 mmol m-2 d-1), and the fraction of total oxalate extracted iron obtained as Fe(II) (0.25-0.52) differed between station and season. Sediments at station Z02 on the eastern LCS, south of Terrebonne Bay, had higher organic matter content and sulfate reduction rates than sediments at Z03, 160 km further west. Sulfate reduction rates were higher in summer than spring at station Z02 but not at Z03 where porewater Mn and Fe concentrations were highest in summer. Porewater Fe2+ concentrations, solid phase oxalate-extractable Fe concentrations, and sediment incubation experiments suggested iron reduction at Z03 may account for 20% or more of organic carbon remineralization. LCS Fe(III) concentrations decreased and sulfate reduction rates increased in model simulations by lowering interfacial dissolved oxygen levels and increasing the rates of organic matter deposited on the sediment surface. Results from this study demonstrate that LCS sedimentary metal oxide cycling may be more important in organic carbon mineralization pathways than previously recognized.

  14. Trinity shoal: a reworked deltaic barrier on Louisiana continental shelf

    SciTech Connect

    Suter, J.R.; Penland, S.; Moslow, T.F.

    1985-02-01

    Abandonment and reworking of deltaic complexes of the Holocene Mississippi River have produced a series of sandy shoals on the muddy Louisiana continental shelf. Trinity shoal, one of these transgressive deposits, is located 30 km offshore of Atchafalaya Bay and the Point Au Fer-March Island shell reefs. Approximately 1000 km of high-resolution uniboom and 3.5 kHz subbottom-profile seismic data, taken in this area in 1983 and 1984, provide the data base for this study. Trinity shoal, associated with the abandoned Maringouin delta complex, is a lunate shore-parallel feature approximately 36 km long and 5-10 km wide. Relief on the shoal ranges from 2 to 3 m, and minimum water depths over the shoal vary from -5 to -2 m. The shoal sand body is from 5 to 7 m thick and is composed largely of parallel to low-angle clinoform reflectors. Several levels of buried fluvial channels, ranging in age from early Wisconsinian to Holocene, are associated with the shoal deposit. The occurrence of channel features within the shoal sand itself suggests the presence of tidal inlets, indicating a possible barrier-island origin for the shoal. The underlying deltaic sediments reach approximately 15 m in thickness and are made up of low-angle clinoform reflectors dipping to the southwest. Distributary, bay-fill, estuarine, and buried oyster-reef deposits can be recognized, making these similar to modern Atchafalaya delta deposits. Continued progradation of the Atchafalaya delta will probably result in burial of the Trinity shoal and Maringouin delta deposits by fine-grained sediments, giving these shoal deposits a high-preservation potential and creating an excellent stratigraphic trap.

  15. Oceanography of the Subtropical Shelf Front Zone in the SW-Atlantic Continental Shelf

    NASA Astrophysics Data System (ADS)

    Muelbert, J. H.; Acha, M.; Berasategui, A.; Bersano, J. G.; Braga, E. S.; Eichler, P.; Garcia, V. M.; Gomez-Erache, M.; Guerrero, R.; Mianzan, H.; Reta, R.; Ramirez, F.

    2005-05-01

    Only physical aspects of the Subtropical Shelf Front (STSF) have been described for the Southwest Atlantic Continental Shelf. The main goal of this paper is to present results of an integrated physical, chemical and biological study at the STSF conducted during the winter of 2003 and summer of 2004. A cross section was established at the historical determined location of the STSF. Nine stations were sampled during the winter cruise and 7 stations during summer. Each section included a series of conductivity-temperature-depth (CTD) stations fitted with dissolved oxygen and turbidity sensors. Selected water samples were filtered and frozen at -20oC for nutrient determination. Samples for chlorophyll were concentrated on filters and these were stored frozen for later processing. Plankton net tows were carried out above and below pycnocline. Surface benthic foraminifera were collected with a bottom snapper. Results revealed that winter was marked by an inner shelf salinity front and the STSF located in the mid-shelf. Inner salinity showed the strong influence of freshwater, with high silicate (71.98 μM), phosphate (2.70 μM), nitrate (1.01 μM), Total Dissolved Nitrogen (22.98 μM) and suspended matter (44.80 mg/L). With distance from the coast and reduction of terrestrial input, subsurface high values of nutrients were associated with SACW upwelling. As a result, chlorophyll a concentration decreased from coastal well-mixed waters, where values up to 3.0 mg.m3 are registered, to offshore waters. Zooplankton abundance and biomass, and ichthyoplankton abundance follows the same trend. Zoo and ichthyoplankton abundance revealed the presence of 3 groups associated to the inner, mid and offshore shelf region. Benthic foraminifera composition suggested that shallow stations are dominated by few large freshwater species, while offshore stations presented smaller forms and higher species diversity. During summer, the halocline extended over the shelf and joined the STSF in

  16. On the difficulty of modeling Circumpolar Deep Water intrusions onto the Amundsen Sea continental shelf

    NASA Astrophysics Data System (ADS)

    Nakayama, Y.; Timmermann, R.; Schröder, M.; Hellmer, H. H.

    2014-12-01

    In the Amundsen Sea, warm Circumpolar Deep Water (CDW) intrudes onto the continental shelf and flows into the ice shelf cavities of the West Antarctic Ice Sheet, resulting in high basal melt rates. However, none of the high resolution global models resolving all the small ice shelves around Antarctica can reproduce a realistic CDW flow onto the Amundsen Sea continental shelf, and previous studies show simulated bottom potential temperature at the Pine Island Ice Shelf front of about -1.8 °C. In this study, using the Finite-Element Sea ice-ice shelf-Ocean Model (FESOM), we reproduce warm CDW intrusions onto the Amundsen Sea continental shelf and realistic melt rates of the ice shelves in West Antarctica. To investigate the importance of horizontal resolution, forcing, horizontal diffusivity, and the effect of grounded icebergs, eight sensitivity experiments are conducted. To simulate the CDW intrusion realistically, a horizontal resolution of about 5 km or smaller is required. The choice of forcing is also important and the cold bias in the NCEP/NCAR reanalysis over the eastern Amundsen Sea prevents warm CDW from intruding onto the continental shelf. On the other hand, the CDW intrusion is not highly sensitive to the strength of horizontal diffusion. The effect of grounded icebergs located off Bear Peninsula is minor, but may act as a buffer to an anomalously cold year.

  17. Low-frequency currents and continental shelf waves in the southern Weddell Sea

    SciTech Connect

    Middleton, J.H.; Foster, T.D.; Foldvik, A.

    1982-07-01

    The salient features of low-frequency current fluctuations, obtained from an analysis of eight current meter records from the continental shelf and slope of the southern Weddell sea, are compared to baroclinic and barotropic theories. A simple baroclinic theory of internal waves is used successfully to predict high-frequency spectral cutoff values from low-frequency velocity ellipse calculations made from the continental slope mooring data. The success of this theory indicates that the higher spectral energy levels observed over the slope compared to the shelf are probably due to baroclinic motions. A barotropic model of free continental shelf waves proposed by Saint-Guily (1976) is adapted for the local topography and the predictions of the model compared to observations. Coherences and phases between moorings separated by 10 and 160 km in the long-shelf direction provide substantial evidence of the existence of shelf waves as predicted by the theory for periods of 3--60 days and for the lowest three modes. For periods of 3--8 days rotary spectral levels indicate anticlockwise rotating current vectors over the shelf as predicted by theory, but for longer periods current vectors rotate clockwise. It is speculated that fluctuations in along-shelf wind stress drive the shelf waves but that the longer period motions are driven directly by the wind stress.

  18. Production and remineralization in continental shelf ecosystems: A test of the SEEP hypothesis

    SciTech Connect

    Rowe, G.T.

    1986-09-01

    The hypothesis that continental shelf ecosystems export a major fraction of the carbon produced by the phytoplankton during the spring bloom was tested during the Shelf Edge Exchange Processes (SEEP) experiment off the northeast US coast in 1984. This study, along with a reanalysis of traditional concepts, leads to the conclusion that only a small fraction of continental shelf phytodetritus is exported across a distinct shelf-slope hydrographic frontal system. What is not consumed in the spring is utilized on the shelf during the ensuing stratified season. More open ended ecosystems may export production more readily. The total benthic standing stocks in terms of organic carbon (macrofauna, meiofauna, and bacteria) have been estimated in the SEEP area. Their preponderance on the continental shelf was partial evidence that little organic matter escapes to the upper continental slope. Measurements of the metabolism of the biota allowed calculation of turnover times of organic detritius and the total biota. The turnover time of detritus increased as grain size decreased, suggesting that fine-grained deposits contain mostly refractory, nonreactive compounds, especially on the deep slope. Turnover times of the total biota were about the same in the coarse versus fine-grained shelf deposits, but a far larger fraction of the turnover was attributed to the bacteria in the fine sediments than in the coarse. On average, about 25% of the primary production appeared to be utilized by the aerobic benthos on the continental shelf in the SEEP area. The role of anaerobes at depth in the sediments remains uncertain.

  19. Quaternary seismic stratigraphy and paleoenvironments on the continental shelf of the East China Sea

    NASA Astrophysics Data System (ADS)

    Liu, Zhen-Xia; Berne, Serge; Saito, Yoshiki; Lericolais, G.; Marsset, T.

    2000-08-01

    Paleoenvironments and stratigraphy have been interpreted from 4380 km of seismic profiling collected during a geological and geophysical cruise on the continental shelf of the East China Sea (ECS) undertaken in 1996. The geophysical data are correlated with a borehole situated on the outer shelf obtained by Shanghai Marine Geology Bureau, indicating that six seismic units have been preserved since oxygen-isotope stage 6, including four regressive-transgressive cycles. Seismic units U2, U3+U4+U5, U6, and U7 are interpreted to correspond respectively to oxygen-isotope stages 1, 3, 5, and 6, implying that sediment partitioning and sequence architecture in the ECS have been controlled by glacio-eustasy and global climate changes. Alternating continental and marine strata corresponding to glaciation and interglaciation are well preserved on the outer shelf of the ECS. Most of the cold environment strata, which formed on the outer shelf during oxygen-isotope stages 2 and 4, are too thin to be recognized on SIG 600J because of resolution, but corresponding erosion surfaces exist. Seismic unit U7 is widespread over the shelf, extending to the continental edge and showing little variation in thickness, as the regression was pronounced and lasted a long time. Thus, U7 can be used as a marker layer for correlation of Quaternary strata on the shelf of the ECS. Post-glacial transgression is obvious in the ECS. Marine strata with varied thickness were developed in the shallow sea of the inner shelf, thinning toward the outer shelf. The continental shelf of the ECS has been influenced by Pacific tide-wave systems for a long time, forming tidal sand-ridge sequences, developed during transgressions, corresponding to oxygen-isotope stages 7 (or 9), 5, 3 and 1.

  20. Holocene stratigraphy of the Alabama inner continental shelf: Influence of shelf sand ridges on determining lithofacies architecture

    SciTech Connect

    Davies, D.J.; Parker, S.J. . Energy and Coastal Geology Div.)

    1993-03-01

    Surface and subsurface distribution of lithofacies from Holocene sediments of the AL inner continental shelf was determined from a series of 59 vibracores and associated surface sediment grab sediments. Five Holocene lithofacies composed of 12 discrete microfacies were delineated based on grain size, color, sedimentary structures, shell content, and fabric of samples. These lithofacies include: (1) Graded Shelly Sand Lithofacies; (2) Clean Sand Lithofacies; (3) Dirty Sand Lithofacies; (4) Biogenic Sediment Lithofacies; and (5) Muddy Sediment Lithofacies. These represent four major depositional environments: The Shelf Sand Sheet Environment (lithofacies 1 and 2); the Sand Ridge Environment (lithofacies 1, 2, and 3); the Bay/Lagoon Environment (lithofacies 3, 4 and 5); and the Muddy Shelf Environment (lithofacies 5). East of the Main Pass of Mobile Bay, the seafloor is composed of a clean Shelf Sand Sheet with oblique shelf sand ridges; Clean Sand and Graded Shelly Sand are the dominant surface sediment types. Coarse shell beds that grade up to quartz sand units (total thickness 0.1 to 3+m) interpreted as tempestites comprise most of the upper portion of the ridges. West of the Pass, the muddier lithofacies (3 and 5) dominate surface samples. Microfacies at depth represent the early Holocene transgressive systems tract; these include the Muddy Shelf Depositional Environment and the filled estuaries and bays of the flooded Pleistocene fluvial valleys represented by the Bay/Lagoon Depositional Environment. The AL inner shelf provides an excellent model of the variability of sedimentation mode in time and space during deposition of a transgressive systems tract. Development of the palimpsest sand sheet/ridge complex progressed on the eastern shelf due to shut off of sediment influx, westward longshore currents, and episodic incidence of major hurricanes. On the western shelf a patchy distribution of muddier sediments developed from input of floodwaters from Mobile Bay.

  1. Variations in sediment texture on the northern Monterey Bay National Marine Sanctuary continental shelf

    USGS Publications Warehouse

    Edwards, B.D.

    2002-01-01

    The storm-protected continental shelf of Monterey Bay, part of the Monterey Bay National Marine Sanctuary, north-central California, is subject to abundant, episodic sediment input from fluvial sources. North of Monterey Bay, conditions of reduced sediment supply combined with the exposed nature of the shelf provide an effective laboratory for studying the contrasting effects of storm- versus fluvial-dominated conditions on modern sedimentation. Textural analyses performed on surface sediment samples collected from more than 380 box cores and MultiCores??? document the existence of a clearly defined mud belt occupying the mid-shelf throughout the region. Inshore sands combined with these mid-shelf muds represent deposits from modern sedimentation processes. In Monterey Bay, where episodic fluvial input from winter storms dominates sedimentation, the mid-shelf mud belt extends across the shelf to the shelf break. North of Monterey Bay, where sediment loads are reduced and both oceanographic and storm processes dominate, the mid-shelf mud belt is bordered by relict sediments occupying the outer shelf. In the study area, mass accumulation rates established by radiochemical studies support the contention that storm-induced along-shelf processes result in northward transport of sediment within the mud belt. The continuity of transport, however, is interrupted by topographic highs which are barriers or inhibitors to sediment transport created by wrench-style tectonics associated with the San Andreas fault system.

  2. Outer Continental Shelf environmental assessment program. Final reports of principal investigators. Volume 33

    SciTech Connect

    Not Available

    1985-07-01

    This ccompilation of five final reports deals with the distribution and dynamics of heavy metals in Alaskan Shelf environments; characterization of organic matter in sediments; distribution of trace elements in bottom sediment of the Northern Bering Sea; aspects of size distributions, clay mineralogy, and geochemistry of sediments of the Beaufort Sea and adjacent deltas; and the natural distribution and dynamics of hydrocarbons on the Alaskan continental shelf.

  3. Source and dispersal of silt on northern Gulf of Mexico Continental Shelf

    SciTech Connect

    Peterson, M.; Mazzullo, J.

    1988-02-01

    The surficial sediment on the continental shelf of the northern Gulf of Mexico is characterized by abundant silty clay which was deposited during the late Pleistocene lowstand and reworked during and after the Holocene transgression. The purposes of this study were to determine the sources of the silt fraction in this surficial sediment by quartz grain roundness and surface texture analysis, and to determine the effects of modern shelf currents upon the distribution of silt.

  4. Water mass circulation on the continental shelf of the Gulf of Cádiz

    NASA Astrophysics Data System (ADS)

    García-Lafuente, Jesús; Delgado, Javier; Criado-Aldeanueva, Francisco; Bruno, Miguel; del Río, Jorge; Miguel Vargas, Juan

    2006-06-01

    Acoustic Doppler Current Profiler data collected during three successive surveys in the Gulf of Cádiz in May-June 2001 have been used to analyse the surface circulation on the continental shelves of the Gulf of Cádiz and how this circulation matches the circulation in the ocean side of the Gulf. The wider and larger eastern continental shelf holds a cyclonic circulation bounded at the south by a shelf-break jet that is identified with the Huelva front. The coastal current that closes the gyre at the north is identified with the warm counterflow mentioned in the literature. Under westerly winds, this counter current recirculates toward the east while recent upwelled water near Cape Santa Maria is advected downstream by the shelf-break jet, leaving the cold signature at the surface that has been identified historically with the Huelva front. Under easterlies, part of the coastal counterflow invades the western continental shelf while the remaining recirculates eastward to close the cyclonic cell. The western continental shelf and slope is occupied by a larger-scale cyclonic eddy that extends into the deep ocean. This eddy has vertical length scale of hundreds of metres and is linked to the general wind forcing in the area. Both cyclonic structures are bounded at the south by a jet that enters in the Gulf of Cádiz moving around the second eddy and eastward to feed the Atlantic inflow through the Strait of Gibraltar.

  5. Cross-shelf and vertical structure of ichthyoplankton assemblages in continental shelf waters of the Southern Gulf of Mexico

    NASA Astrophysics Data System (ADS)

    Espinosa-Fuentes, M. L.; Flores-Coto, C.

    2004-02-01

    The horizontal and vertical variation of ichthyoplankton assemblages in continental shelf waters of the Southern Gulf of Mexico was studied during an annual cycle (1994-1995) at 22 stations distributed across four transects located off the main fluvio-lagoon systems of the area. Samples were collected from five levels of the water column, from the surface to a depth of 105 m. The Bray-Curtis Dissimilarity Index identified five assemblages: Coastal, Inner Neritic, Outer Neritic, Oceanic and a Transition Group. The main species of each assemblage reflected the habitat, season, and spawning area of adult organisms. The Coastal Assemblage occupied the uppermost water column levels of the most nearshore stations. The Oceanic Assemblage was restricted to the deepest samplings of the stations of the outer shelf and the Neritic Assemblages were located on the continental shelf between the Coastal and Oceanic Assemblages, embracing all the sampling levels in some periods. Variation in composition, location and abundance of larvae in each assemblage was determined by a series of physical processes that act at different temporal and spatial scales, especially the mixing process generated by the wind stress and continental water discharges acting at a mesoscale that influences the distribution of the assemblages along the whole continental shelf as well as a fine scale affecting the composition and vertical distribution of organisms in a more reduced area of just tens of meters in the water column. Canonical Correspondence Analysis revealed that the depth of the sample, the potential energy, and the temperature generated the greatest variability in the system. Vertical and horizontal salinity gradients play a determinant role in delimiting the Coastal and Neritic Assemblages.

  6. Circulation and exchange processes over the continental shelf and slope. Final report

    SciTech Connect

    Csanady, G.T.

    1988-12-31

    The theme of the work during the past triennium has been the SEEP experiment, data interpretation and modeling related to the goals of the experiment, and was characterized by increasing cooperation with colleagues from other disciplines. The theoretical contributions dealt with shelf-slope interaction, the dynamics and climatology of currents over the continental slope, and the behavior of fate of organic particles. Observational papers discussed various exchange mechanisms at the shelf edge, with special attention to particle exchange, and the quiescence of currents over the mid continental slope which is presumably responsible for the accumulation of organic particles.

  7. An instrument system for long-term sediment transport studies on the continental shelf

    USGS Publications Warehouse

    Butman, Bradford; Folger, David W.

    1979-01-01

    A bottom-mounted instrument system has been designed and built to monitor processes of bottom sediment movement on the continental shelf. The system measures bottom current speed and direction, pressure, temperature, and light transmission and photographs the bottom. The system can be deployed for periods of 2–6 months to monitor intermitent processes of sediment movement such as storms and to assess seasonal variability. Deployments of the system on the U.S. east coast continental shelf show sediment resuspension and changes in bottom microtopography due to surface waves, tidal currents, and storms.

  8. Onshore-offshore movement of jumbo squid (Dosidicus gigas) on the continental shelf

    NASA Astrophysics Data System (ADS)

    Stewart, Julia S.; Gilly, William F.; Field, John C.; Payne, John C.

    2013-10-01

    Jumbo squid (Dosidicus gigas) have greatly extended their range in the California Current System, where they forage on a variety of ecologically and economically important species that inhabit both coastal and offshore mesopelagic regions. Swimming abilities and behavior are important factors in assessing the impacts of this range expansion, particularly in regard to foraging in conjunction with onshore-offshore movement over the continental shelf. Here we describe a study of horizontal movements by jumbo squid along and across the continental shelf off Washington, USA, using acoustic tags in association with the Census of Marine Life's Pacific Ocean Shelf Tracking Program (POST) receiver arrays. We detected frequent movements along the shelf break, movement onto the shelf at night, and no evidence of movement as a cohesive school. Our results demonstrate feasibility of using acoustic tags and arrays to document horizontal movements of jumbo squid along and across the continental shelf. This is important in order to determine how those movements overlap with those of other ecologically and commercially important fish species.

  9. Stratigraphic framework and heavy minerals of the continental shelf of Onslow and Long Bays, North Carolina

    USGS Publications Warehouse

    Hoffman, Charles W.; Grosz, Andrew E.; Nickerson, John G.

    1999-01-01

    One hundred fourteen vibracores from the Atlantic continental shelf offshore of southeastern North Carolina were opened, described, and processed over several contract years (years 6-9) of the Minerals Management Service-Association of American State Geologists Continental Margins program. Reports for years 9 and 10 of the program compiled the results of the work and assembled the data for release as an interactive CD-ROM report, respectively. The continental shelf of Onslow and Long Bays consists predominantly of outcropping Cretaceous through late Tertiary geologic units. Nearshore these units are covered and incised by late Tertiary and Quaternary units. From oldest to youngest, formally recognized geologic units mapped as part of this study are the Late Cretaceous Peedee Formation-a muddy, fine- to medium-grained quartz sand with trace amounts of glauconite and phosphate; the Paleocene Beaufort Formation-a muddy, fine- to medium-grained glauconitic quartz sand with locally occurring turritelid-mold biosparrudite; the middle Eocene Castle Hayne Formation-a sandy bryozoan biomicrudite and biosparrudite; the Oligocene River Bend Formation-a sandy molluscan-mold biosparrudite; and the Miocene Pungo River Formation-a medium-grained, poorly sorted slightly shelly phosphatic sand. Informal units include a very widespread, unnamed fine- to very fine grained, well-sorted, dolomitic muddy quartz sand that is biostratigraphically equivalent to the Oligocene River Bend Formation; several large valley-fill lithosomes composed of biomicrudite, biomicrite, and biosparrudite of Plio/Pleistocene age; muddy, shelly sands and silty clays of Pliocene, Pleistocene, or mixed Plio/Pleistocene age; and loose, slightly shelly, medium- to coarse-grained sands assigned a Holocene age. Heavy minerals (SG > 2.96) comprise an average of 0.54 wt% (on a bulk-sample basis) of the sediments in 306 samples derived from the 114 vibracores. Heavy-mineral content ranges from 3 in the sediments. The

  10. Sea ice and oceanic processes on the Ross Sea continental shelf

    NASA Technical Reports Server (NTRS)

    Jacobs, S. S.; Comiso, J. C.

    1989-01-01

    The spatial and temporal variability of Antarctic sea ice concentrations on the Ross Sea continental shelf have been investigated in relation to oceanic and atmospheric forcing. Sea ice data were derived from Nimbus 7 scanning multichannel microwave radiometer (SMMR) brightness temperatures from 1979-1986. Ice cover over the shelf was persistently lower than above the adjacent deep ocean, averaging 86 percent during winter with little month-to-month of interannual variability. The large spring Ross Sea polynya on the western shelf results in a longer period of summer insolation, greater surface layer heat storage, and later ice formation in that region the following autumn.

  11. 76 FR 40725 - Approval of Outer Continental Shelf (OCS) Permit Issued to Cape Wind Associates, LLC (EPA Permit...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-07-11

    ... offshore renewable wind energy project in federal waters off the coast of Massachusetts. DATES: Effective... AGENCY Approval of Outer Continental Shelf (OCS) Permit Issued to Cape Wind Associates, LLC (EPA Permit... Outer Continental Shelf (OCS) air permit decision regarding Cape Wind Associates, LLC (Cape Wind)....

  12. 77 FR 3771 - Notice of Issuance of Final Outer Continental Shelf Air Permit for Shell Offshore, Inc.

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-01-25

    ... From the Federal Register Online via the Government Publishing Office ENVIRONMENTAL PROTECTION AGENCY Notice of Issuance of Final Outer Continental Shelf Air Permit for Shell Offshore, Inc. AGENCY... on November 30, 2011, EPA issued a final Outer Continental Shelf (OCS) air permit for Shell...

  13. 77 FR 5039 - Accommodation Service Provided on Vessels Engaged in U.S. Outer Continental Shelf Activities

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-02-01

    ... SECURITY Coast Guard Accommodation Service Provided on Vessels Engaged in U.S. Outer Continental Shelf... providing accommodation service on the U.S. Outer Continental Shelf. DATES: Comments and related material... Act notice regarding our public dockets in the January 17, 2008, issue of the Federal Register (73...

  14. 77 FR 39164 - Safety Zone; KULLUK, Outer Continental Shelf Mobile Offshore Drilling Unit (MODU), Beaufort Sea, AK

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-07-02

    ... SECURITY Coast Guard 33 CFR Part 147 RIN 1625-AA00 Safety Zone; KULLUK, Outer Continental Shelf Mobile...; KULLUK, Outer Continental Shelf Mobile Offshore Drilling Unit (MODU), Beaufort Sea, Alaska'' in the Federal Register (77 FR 10711). The NPRM included a 30- day comment period. We received 2...

  15. 76 FR 53481 - Outer Continental Shelf, Alaska OCS Region, Chukchi Sea Planning Area, Oil and Gas Lease Sale 193

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-08-26

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF THE INTERIOR Bureau of Ocean Energy Management, Regulation and Enforcement Outer Continental Shelf, Alaska OCS Region... Continental Shelf (OCS) Oil and Gas Lease Sale 193, Chukchi Sea, Alaska (OCS EIS/EA BOEMRE 2011-041)....

  16. 77 FR 10711 - Safety Zone; KULLUK, Outer Continental Shelf Mobile Offshore Drilling Unit (MODU), Beaufort Sea, AK

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-02-23

    ... SECURITY Coast Guard 33 CFR Part 147 RIN 1625-AA00 Safety Zone; KULLUK, Outer Continental Shelf Mobile... prospects located in the Beaufort Sea Outer Continental Shelf, Alaska, from 12:01 a.m. on July 1, 2012... Federal Register (73 FR 3316). Public Meeting The Coast Guard does not plan to hold a public meeting....

  17. 76 FR 70156 - Proposed 5-Year Outer Continental Shelf (OCS) Oil and Gas Leasing Program for 2012-2017

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-11-10

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF THE INTERIOR Bureau of Ocean Energy Management Proposed 5-Year Outer Continental Shelf (OCS) Oil and Gas Leasing... Continental Shelf Lands Act (OCSLA) specifies a multi-step process of consultation and analysis that must...

  18. 76 FR 48861 - Notice of Issuance of Final Outer Continental Shelf Air Permit for Anadarko Petroleum Corporation

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-08-09

    ... From the Federal Register Online via the Government Publishing Office ] ENVIRONMENTAL PROTECTION AGENCY Notice of Issuance of Final Outer Continental Shelf Air Permit for Anadarko Petroleum Corporation... announce that on June 15, 2011, EPA issued a final Outer Continental Shelf (OCS) air permit for...

  19. Origin and extent of fresh paleowaters on the Atlantic continental shelf, USA.

    PubMed

    Cohen, Denis; Person, Mark; Wang, Peng; Gable, Carl W; Hutchinson, Deborah; Marksamer, Andee; Dugan, Brandon; Kooi, Henk; Groen, Koos; Lizarralde, Daniel; Evans, Robert L; Day-Lewis, Frederick D; Lane, John W

    2010-01-01

    While the existence of relatively fresh groundwater sequestered within permeable, porous sediments beneath the Atlantic continental shelf of North and South America has been known for some time, these waters have never been assessed as a potential resource. This fresh water was likely emplaced during Pleistocene sea-level low stands when the shelf was exposed to meteoric recharge and by elevated recharge in areas overrun by the Laurentide ice sheet at high latitudes. To test this hypothesis, we present results from a high-resolution paleohydrologic model of groundwater flow, heat and solute transport, ice sheet loading, and sea level fluctuations for the continental shelf from New Jersey to Maine over the last 2 million years. Our analysis suggests that the presence of fresh to brackish water within shallow Miocene sands more than 100 km offshore of New Jersey was facilitated by discharge of submarine springs along Baltimore and Hudson Canyons where these shallow aquifers crop out. Recharge rates four times modern levels were computed for portions of New England's continental shelf that were overrun by the Laurentide ice sheet during the last glacial maximum. We estimate the volume of emplaced Pleistocene continental shelf fresh water (less than 1 ppt) to be 1300 km(3) in New England. We also present estimates of continental shelf fresh water resources for the U.S. Atlantic eastern seaboard (10(4) km(3)) and passive margins globally (3 x 10(5) km(3)). The simulation results support the hypothesis that offshore fresh water is a potentially valuable, albeit nonrenewable resource for coastal megacities faced with growing water shortages. PMID:19754848

  20. Origin and extent of fresh paleowaters on the Atlantic continental shelf, USA

    USGS Publications Warehouse

    Cohen, D.; Person, M.; Wang, P.; Gable, C.W.; Hutchinson, D.; Marksamer, A.; Dugan, B.; Kooi, H.; Groen, K.; Lizarralde, D.; Evans, R.L.; Day-Lewis, F. D.; Lane, J.W., Jr.

    2010-01-01

    While the existence of relatively fresh groundwater sequestered within permeable, porous sediments beneath the Atlantic continental shelf of North and South America has been known for some time, these waters have never been assessed as a potential resource. This fresh water was likely emplaced during Pleistocene sea-level low stands when the shelf was exposed to meteoric recharge and by elevated recharge in areas overrun by the Laurentide ice sheet at high latitudes. To test this hypothesis, we present results from a high-resolution paleohydrologic model of groundwater flow, heat and solute transport, ice sheet loading, and sea level fluctuations for the continental shelf from New Jersey to Maine over the last 2 million years. Our analysis suggests that the presence of fresh to brackish water within shallow Miocene sands more than 100 km offshore of New Jersey was facilitated by discharge of submarine springs along Baltimore and Hudson Canyons where these shallow aquifers crop out. Recharge rates four times modern levels were computed for portions of New England's continental shelf that were overrun by the Laurentide ice sheet during the last glacial maximum. We estimate the volume of emplaced Pleistocene continental shelf fresh water (less than 1 ppt) to be 1300 km3 in New England. We also present estimates of continental shelf fresh water resources for the U.S. Atlantic eastern seaboard (104 km3) and passive margins globally (3 ?? 105 km3). The simulation results support the hypothesis that offshore fresh water is a potentially valuable, albeit nonrenewable resource for coastal megacities faced with growing water shortages. ?? 2009 National Ground Water Association.

  1. Continental shelf landscapes of the southeastern United States since the last interglacial

    NASA Astrophysics Data System (ADS)

    Harris, M. Scott; Sautter, Leslie Reynolds; Johnson, Kacey L.; Luciano, Katherine E.; Sedberry, George R.; Wright, Eric E.; Siuda, Amy N. S.

    2013-12-01

    The wide, sediment-starved continental shelf and modern coastal areas of the southeastern United States retain well-preserved but scattered remnants of a submerged paleolandscape. This paper presents a conceptual model of stratigraphic deposition and landscape formation since the last interglacial on the continental shelf of South Carolina, with portions of North Carolina, Georgia, and Florida (USA). Data for this study include multibeam bathymetry surveys, sidescan sonar mosaics, high-resolution subbottom profiles, and ground-truth surveys from - 250 m to the modern tidewater region. Four bathymetric zones are recognized with eleven landforms and landform indicators. The described zones range in depths from the modern shoreline, across the shelf, and over the shelf edge to - 250 m MSL. Relative sea level curves are presented for the area and discussed in conjunction with cultural and climatic events. The potential for preservation of Paleoamerican sites is high at the shelf edge between - 130 m and - 45 m, with Archaic and later occupations likely in depths of less than - 25 m. Prominent vantage points for Paleoamericans (> 11 kya) would have existed at the shelf edge, and tidewater resources would have been available nearby for a period of almost 6 ka. Rapid transgression rates (> 60 km/ka) after the sea level rose over the shelf edge make preservation of tidewater sites less likely on the outer and middle shelf. Searches for the earliest Paleoamericans should focus on promontories at the edge of the shelf and along future discoveries of paleoincisions on the shelf. Mapping and delineating this paleolandscape and associated unconsolidated sedimentary deposits interspersed with rocky plains and ledges will continue to be a priority to marine archeologists, coastal managers, fishery scientists, and marine spatial planners over the next several decades.

  2. Suspended particulate layers and internal waves over the southern Monterey Bay continental shelf: An important control on shelf mud belts?

    NASA Astrophysics Data System (ADS)

    Cheriton, Olivia M.; McPhee-Shaw, Erika E.; Shaw, William J.; Stanton, Timothy P.; Bellingham, James G.; Storlazzi, Curt D.

    2014-01-01

    Physical and optical measurements taken over the mud belt on the southern continental shelf of Monterey Bay, California documented the frequent occurrence of suspended particulate matter features, the majority of which were detached from the seafloor, centered 9-33 m above the bed. In fall 2011, an automated profiling mooring and fixed instrumentation, including a thermistor chain and upward-looking acoustic Doppler current profiler, were deployed at 70 m depth for 5 weeks, and from 12 to 16 October a long-range autonomous underwater vehicle performed across-shelf transects. Individual SPM events were uncorrelated with local bed shear stress caused by surface waves and bottom currents. Nearly half of all observed SPM layers occurred during 1 week of the study, 9-16 October 2011, and were advected past the fixed profiling mooring by the onshore phase of semidiurnal internal tide bottom currents. At the start of the 9-16 October period, we observed intense near-bed vertical velocities capable of lifting particulates into the middle of the water column. This "updraft" event appears to have been associated with nonlinear adjustment of high-amplitude internal tides over the mid and outer shelf. These findings suggest that nonlinear internal tidal motions can erode material over the outer shelf and that, once suspended, this SPM can then be transported shoreward to the middle and shallow sections of the mud belt. This represents a fundamental broadening of our understanding of how shelf mud belts may be built up and sustained.

  3. Suspended particulate layers and internal waves over the southern Monterey Bay continental shelf: an important control on shelf mud belts?

    USGS Publications Warehouse

    Cheriton, Olivia M.; McPhee-Shaw, Erika E.; Shaw, William J.; Stanton, Timothy P.; Bellingham, James G.; Storlazzi, Curt D.

    2014-01-01

    Physical and optical measurements taken over the mud belt on the southern continental shelf of Monterey Bay, California documented the frequent occurrence of suspended particulate matter features, the majority of which were detached from the seafloor, centered 9–33 m above the bed. In fall 2011, an automated profiling mooring and fixed instrumentation, including a thermistor chain and upward-looking acoustic Doppler current profiler, were deployed at 70 m depth for 5 weeks, and from 12 to 16 October a long-range autonomous underwater vehicle performed across-shelf transects. Individual SPM events were uncorrelated with local bed shear stress caused by surface waves and bottom currents. Nearly half of all observed SPM layers occurred during 1 week of the study, 9–16 October 2011, and were advected past the fixed profiling mooring by the onshore phase of semidiurnal internal tide bottom currents. At the start of the 9–16 October period, we observed intense near-bed vertical velocities capable of lifting particulates into the middle of the water column. This “updraft” event appears to have been associated with nonlinear adjustment of high-amplitude internal tides over the mid and outer shelf. These findings suggest that nonlinear internal tidal motions can erode material over the outer shelf and that, once suspended, this SPM can then be transported shoreward to the middle and shallow sections of the mud belt. This represents a fundamental broadening of our understanding of how shelf mud belts may be built up and sustained.

  4. Novel decomposition products of chlorophyll- a in continental shelf (Louisiana shelf) sediments: formation and transformation of carotenol chlorin esters

    NASA Astrophysics Data System (ADS)

    Chen, Nianhong; Bianchi, Thomas S.; Bland, John M.

    2003-06-01

    In April 2000, we collected box cores from five stations along a cross-shelf transect on the Louisiana (LA) continental shelf. Novel esters of carotenols and chlorins (carotenoid chlorin esters, CCEs), which are highly specific grazing markers, were identified in surface and deep sediments (>10 cm) from the LA shelf. Chlorophyll- a inventory indicated that CCEs are one of the major decay products of chlorophyll- a in shelf sediments. Abundances of total CCEs (9-18%) in surface sediments along the cross-shelf transect were comparable to the abundance of pheophytin- a, pyropheophytin- a, and total steryl chlorin esters (SCEs). Prior work has identified four CCEs which have dehydrated fucoxanthin/fucoxanthinol as a substitute alcohol of phytol. We report on four newly identified CCEs associated with nondehydrated fuxocanthin/fucoxanthinol esterified to (pyro)pheophorbide- a. These nondehydrated CCEs were generally present in lower concentrations than their dehydrated counterparts, but were detectable by atmospheric pressure chemical ionization (APCI) mass spectrometry coupled with high-performance liquid chromatography (HPLC). We attributed differences between this study and previous work to the time allowed for predepositional decay and grazing processes to occur. The rapid sedimentation of CCEs in the shallow water column (ca. 10 m) on the LA shelf allowed for effective burial of all CCEs compared to the deeper water column regions sampled by previous work. This speculation is supported by the fact that the concentrations of CCEs with nondehydrated fucoxanthin/fucoxanthinol were extremely low in sediments from the site on the outer LA shelf with a deeper (253 m) water column. We also tentatively identified an additional CCE and its isomer as fucoxanthinol didehydrate pyropheophorbide- a ester. We suggest that the formation and transformation of CCEs are primarily controlled by the following three biologically mediated reactions: demethoxycarbonylation, dehydration

  5. Impacts of Outer Continental Shelf (OCS) development on recreation and tourism. Volume 4. User's manual

    SciTech Connect

    Not Available

    1987-04-01

    The final report for the project is presented in five volumes. The project sought to determine the impact of Outer Continental Shelf development on recreation and tourism in California. This volume is the User's Guide. It includes the following topics: Introduction and Summary Guide; Input Data Files; Gravity Model Programs; Economic Effects Model Programs; Consumer Surplus Model Programs; References; and Appendices.

  6. Impacts of Outer Continental Shelf (OCS) development on recreation and tourism. Volume 5. Program logic manual

    SciTech Connect

    Not Available

    1987-04-01

    The final report for the project is presented in five volumes. This volume is the Programmer's Manual. It covers: a system overview, attractiveness component of gravity model, trip-distribution component of gravity model, economic-effects model, and the consumer-surplus model. The project sought to determine the impact of Outer Continental Shelf development on recreation and tourism.

  7. 76 FR 5189 - BOEMRE Information Collection Activities: 1010-0081, Operations in the Outer Continental Shelf...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-01-28

    ...To comply with the Paperwork Reduction Act of 1995 (PRA), we are notifying the public that we have submitted to OMB an information collection request (ICR) to renew approval of the paperwork requirements in the regulations under 30 CFR 282, Operations in the Outer Continental Shelf for Minerals Other than Oil, Gas, and Sulphur. This notice also provides the public a second opportunity to......

  8. Reactive Iron and Iron-Reducing Bacteria in Louisiana Continental Shelf Sediments

    EPA Science Inventory

    The Mississippi and Atchafalaya Rivers release sediments containing 15 x 106 t of iron onto the Louisiana continental shelf (LCS) each year. Iron oxides reaching the seafloor may be utilized as electron acceptors by iron-reducing bacteria for organic matter oxidation or become r...

  9. A PROBABILISTIC SURVEY OF FISH TISSUE CONTAMINATION FROM THE CONTINENTAL SHELF OF THE US WEST COAST

    EPA Science Inventory

    A probabilistic survey of environmental condition of the continental shelf of the US West Coast was conducted in 2003 by the US EPA National Coastal Assessment (NCA), with collaboration by the NOAA National Marine Fisheries Service. Metals and organic contaminants were analyzed ...

  10. Nutrient distributions, transports, and budgets on the inner margin of a river-dominated continental shelf

    EPA Science Inventory

    Physical and biogeochemical processes determining the distribution and fate of nutrients delivered by the Mississippi and Atchafalaya rivers to the inner (<50 m depth) Louisiana continental shelf (LCS) were examined using a three-dimensional hydrodynamic model of the LCS and obse...

  11. 76 FR 70156 - Draft Programmatic Environmental Impact Study (PEIS) for Proposed 5-Year Outer Continental Shelf...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-11-10

    ... Bureau of Ocean Energy Management Draft Programmatic Environmental Impact Study (PEIS) for Proposed 5-Year Outer Continental Shelf (OCS) Oil and Gas Leasing Program for 2012-2017 AGENCY: Bureau of Ocean... FURTHER INFORMATION CONTACT: Bureau of Ocean Energy Management, Headquarters, 381 Elden Street,...

  12. 78 FR 48180 - Consolidation of Officer in Charge, Marine Inspection For Outer Continental Shelf Activities...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-08-07

    ... SECURITY Coast Guard Consolidation of Officer in Charge, Marine Inspection For Outer Continental Shelf Activities; Eighth Coast Guard District AGENCY: Coast Guard, DHS. ACTION: Notice and request for comments. SUMMARY: The Coast Guard is considering establishing a single Officer in Charge, Marine Inspection...

  13. Outer continental shelf environmental-assessment program. Final reports of principal investigators. Volume 68

    SciTech Connect

    Not Available

    1990-08-01

    The contents of this study include the following: biological reconnaissance of Boulder Island Shoal in western Camden Bay, Beaufort Sea, Alaska; the Chukchi Sea continental shelf: benthos-environmental interactions; ecological assessment of sublittoral plant communities in the northern Gulf of Alaska; and ecology of unconsolidated beaches in Lower Cook Inlet.

  14. 78 FR 45965 - Research Lease on the Outer Continental Shelf (OCS) Offshore Virginia, Request for Competitive...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-07-30

    ... Bureau of Ocean Energy Management Research Lease on the Outer Continental Shelf (OCS) Offshore Virginia... FR 44150-44156). The area identified for potential commercial wind leasing in the PSN was delineated... Environmental Assessment (EA) (76 FR 40926). Among the comments received on the draft EA was a letter...

  15. 76 FR 13205 - Notice on Outer Continental Shelf Oil and Gas Lease Sales

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-03-10

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF THE INTERIOR Bureau of Ocean Energy Management, Regulation and Enforcement Notice on Outer Continental Shelf Oil and.... Correction In the Federal Register of February 9, 2011, in FR Doc. 2011-2791, on page 7230, in the...

  16. 76 FR 7230 - Notice on Outer Continental Shelf Oil and Gas Lease Sales

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-02-09

    ... From the Federal Register Online via the Government Publishing Office ] DEPARTMENT OF THE INTERIOR Bureau of Ocean Energy Management, Regulation and Enforcement Notice on Outer Continental Shelf Oil and.... Correction In the Federal Register of January 24, 2011, in FR Doc. 2011-1319, on page 4129, correct...

  17. 75 FR 20859 - Outer Continental Shelf (OCS) Policy Committee; Notice and Agenda for Meeting

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-04-21

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF THE INTERIOR Minerals Management Service Outer Continental Shelf (OCS) Policy Committee; Notice and Agenda for Meeting AGENCY: Minerals Management Service (MMS), Interior. ACTION: Notice of Meeting. SUMMARY: The OCS...

  18. 78 FR 5836 - Adjustment of Service Fees for Outer Continental Shelf Activities

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-01-28

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF THE INTERIOR Bureau of Ocean Energy Management Adjustment of Service Fees for Outer Continental Shelf Activities... updated in 2008, with Federal Register Notice 73 FR 49943. BOEM is now adjusting various cost...

  19. The application of Seasat-1 radar altimetry to continental shelf circulation modeling

    NASA Technical Reports Server (NTRS)

    Cornillon, P.; Reed, M.; Spaulding, M.; Swanson, C.

    1980-01-01

    Seasat-1 radar altimetry data have been used to verify a continental shelf circulation model subjected to tidal forcing on the open boundary. The model makes use of the semi-implicit mode of time integration, removing the surface gravity wave time step restriction. Both the altimetry and the model predictions are compared with empirically determined tidal fluctuations and generally good agreement is obtained.

  20. Application of remote sensing to study nearshore circulation. [and the continental shelf

    NASA Technical Reports Server (NTRS)

    Zeigler, J.; Lobecker, R.; Stauble, D.; Welch, C.; Haas, L.; Fang, C. S.

    1974-01-01

    The research to use remote sensing techniques for studying the continental shelf is reported. The studies reported include: (1) nearshore circulation in the vincinity of a natural tidal inlet; (2) identification of indicators of biological activity; (3) remote navigation system for tracking free drifting buoys; (4) experimental design of an estuaring tidal circulation; and (5) Skylab support work.

  1. 75 FR 82055 - Commercial Leasing for Wind Power on the Outer Continental Shelf (OCS) Offshore Massachusetts...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-12-29

    ...The Bureau of Ocean Energy Management, Regulation and Enforcement (BOEMRE) invites submissions describing interest in obtaining one or more commercial leases for the construction of a wind energy project(s) on the Outer Continental Shelf (OCS) offshore Massachusetts. BOEMRE will use the responses to this RFI to gauge specific interest in commercial development of OCS wind resources in the area......

  2. Interpretation of graphic data on potential geologic hazards on the southeastern United States Atlantic continental shelf

    USGS Publications Warehouse

    Popenoe, Peter; Butman, Bradford; Paull, Charles K.; Ball, Mahlon M.; Pfirman, Stephanie L.

    1981-01-01

    This report presents and analyzes seismic-survey data and bottom-instrument data as they pertain to a regional assessment of potential geologic hazards and other constraints to petroleum exploration and development on the southeastern United States Continental Shelf (see fig. 1).  

  3. 78 FR 14917 - Outer Continental Shelf Air Regulations Consistency Update for California

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-03-08

    ...EPA is finalizing the update of the Outer Continental Shelf (``OCS'') Air Regulations proposed in the Federal Register on October 9, 2012. Requirements applying to OCS sources located within 25 miles of States' seaward boundaries must be updated periodically to remain consistent with the requirements of the corresponding onshore area (``COA''), as mandated by the Clean Air Act, as amended in......

  4. 75 FR 61511 - Intent To Prepare a Supplemental Environmental Impact Statement: Outer Continental Shelf, Alaska...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-10-05

    ...The Bureau of Ocean Energy Management, Regulation and Enforcement (BOEMRE) is giving notice of its intent to publish a Supplemental Environmental Impact Statement for Outer Continental Shelf (OCS) Oil and Gas Lease Sale 193 in the Chukchi Sea Planning Area, Alaska. This Supplementary EIS will provide new analysis in response to a remand by the United States District Court for the District of......

  5. Assessment of the US Outer Continental Shelf Environmental Studies Program. 4. Lessons and opportunities. Final report

    SciTech Connect

    Not Available

    1993-01-01

    The report is the last report in a series of six reports prepared by the NRC Committee to Review the Outer Continental Shelf Environmental Studies Program. The committee's conclusions and recommendations in this final report are based on its analyses of published documents and those provided by MMS; on the briefings it has received; on its earlier reports; and on its own deliberations.

  6. 77 FR 24734 - Outer Continental Shelf (OCS) Renewable Energy Program Leasing for Marine Hydrokinetic Technology...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-04-25

    ... Bureau of Ocean Energy Management Outer Continental Shelf (OCS) Renewable Energy Program Leasing for... and information on the public session can be found online at: http://www.boem.gov/Renewable-Energy... Renewable Energy Programs, 381 Elden Street, HM 1328, Herndon, Virginia 20170-4817, (703) 787-1340...

  7. Atlantic update, July 1986--June 1990: Outer Continental Shelf oil and gas activities

    SciTech Connect

    Karpas, R.M.; Gould, G.J.

    1990-10-01

    This report describes outer continental shelf oil and gas activities in the Atlantic Region. This edition of the Atlantic Update includes an overview of the Mid-Atlantic Planning Area and a summary of the Manteo Prospect off-shore North Carolina. 6 figs., 8 tabs.

  8. Mineral resource management of the Outer Continental Shelf : leasing procedures, evaluation of resources, and supervision of production operations on leased lands of the Outer Continental Shelf

    USGS Publications Warehouse

    Adams, Maurice V.; John, C.B.; Kelly, R.F.; LaPointe, A.E.; Meurer, R.W.

    1975-01-01

    An important function of the Geological Survey is the evaluation and management of the mineral resources of the Outer Continental Shelf, particularly with respect to oil and gas, salt, and sulfur. Production of oil and gas from the Outer Continental Shelf of the United States has increased substantially over the past 20 years and represents an increasing percentage of total United States production. As discovery of major onshore production of oil and gas has become more difficult, the search has moved into the surrounding waters where submerged sedimentary formations are conducive to the accumulation of oil and gas. Increased energy demands of recent years have accelerated the pace of offshore operations with a corresponding improvement in technology as exploration and development have proceeded farther from shore and into deeper water. While improved technology and enforcement of more stringent regulations have made offshore operations safer, it is unrealistic to believe that completely accident-free operations can ever be achieved. Only slightly more than six percent of the world's continental terrace is adjacent to the United States, but less than one percent has been explored for oil and gas. Since the lead time for the development of offshore oil and gas resources can be as much as a decade, they do not provide an immediate energy supply but should be viewed in the light of a near-term source with a potential of becoming a medium-range source of supply pending the development of alternative energy sources. Revenues from the Outer Continental Shelf are deposited to the general fund of the United States Treasury. A major portion of these funds is allocated to the Land and Water Conservation Fund, the largest Federal grant-in-aid program of assistance to States, counties, and cities for the acquisition and development of public parks, open space, and recreation lands and water.

  9. Source and dispersal of silt on northern Gulf of Mexico continental shelf

    SciTech Connect

    Peterson, M.; Mazzullo, J.

    1988-01-01

    The surficial sediment on the continental shelf of the northern Gulf of Mexico is characterized by abundant silty clay which was deposited during the late Pleistocene lowstand and reworked during and after the Holocene transgression. The purposes of this study were to determine the sources of the silt fraction in this surficial sediment by quartz grain roundness and surface texture analysis, and to determine the effects of modern shelf currents upon the distribution of silt. Areal variations in quartz grain roundness and surface texture define six silt provinces on the northern Gulf of Mexico continental shelf. The Mississippi province is the largest province and stretches from the Chandeleur Islands to Matagorda Bay. It is characterized by a mixture of rounded grains that were derived from the sedimentary rocks of the Gulf coastal plain and the Mid-Continent, and angular, fractured grains that were derived from glacial deposits in the northern United States. A comparison of the areal distribution of these six provinces with the late Pleistocene paleogeography of the continental shelf shows evidence for varying degrees of shore-parallel transport of silt by modern shelf currents.

  10. Tidal energy fluxes and dissipation on the European continental shelf

    NASA Astrophysics Data System (ADS)

    Davies, Alan M.; Kwong, Simon C. M.

    2000-09-01

    The spatial distribution of the energy flux, energy dissipation, current magnitude, and surface elevation amplitude of the major tidal constituents over the northwest European shelf are examined in detail. These distributions are obtained from the harmonic analysis of a 6 month three-dimensional simulation of 28 tidal constituents. The model currents are validated by a comparison of computed tidal harmonics against those derived from a harmonic analysis of up to 278 current time series. A similar comparison is performed for tidal elevations based on 257 tide gauges. Calculations show that for the most significant tidal constituents (e.g., M2, S2 and K2) there is a major energy flux in the deep water along the shelf edge off the northwest of Scotland, with some energy leaking onto the shelf and into the North Sea. A second source of energy is across the shelf edge at the southern end of the Celtic Sea, with this energy flux propagating into the Irish Sea and southern North Sea, where the majority of the energy is dissipation in the shallow regions. Significantly different distributions are found for the diurnal and shallow water constituents, and the spatial distributions of energy flux and dissipation of the various constituents are considered. The accuracy of separating tidal current harmonics using model data of less than a synodic period is examined with reference to the S2 and K2 tide. Calculations suggest that the accuracy of computed currents comparable to those obtained from observations can be obtained from an analysis of a 60 day period compared with the synodic period for S2 and K2 of 182 days, a significant saving in computer time.

  11. Flux of energy and essential elements through the continental shelf ecosystem. Progress report

    SciTech Connect

    Pomeroy, L.R.

    1981-11-30

    There are three distinct but not mutually exclusive areas of research in this contract, studies of intrusions of the west wall of the Gulf Stream onto the outer continental shelf, studies of the flux of materials across nearshore density fronts, and advances in understanding of the planktonic food web of the continental shelf. Studies of frontal events on the outer and inner continental shelf involve distinctive physical and chemical regimes and have proven to require distinctive biological approaches. The studies of the food web run through our work on both of the frontal regimes, but certain aspects have become subjects in their own right. We have developed a simulation model of the flux of energy through the continental shelf food web which we believe to be more realistic than previous ones of its type. We have examined several of the many roles of dissolved organic compounds in sea water which originate either from release by phytoplankton, digestive processes or metabolites of zooplankton, or extracellular digestion of microorganisms. Methods have been developed under this contract to measure both the chelating capacity of naturally occurring organic materials and the copper concentration in the water. It has been possible to characterize the effects, both toxic and stimulatory, of copper on photosynthesis of naturally occurring phytoplankton populations. It is possible to characterize in considerable detail the course of biological events associated with meanders of the Gulf Stream. We are now in a position to explain the limits to biological productivity of the outer continental shelf of the southeastern US and the reasons why that biological production moves through the food web in the characteristic way that it does.

  12. High-magnesium calcite dissolution in tropical continental shelf sediments controlled by ocean acidification.

    PubMed

    Haese, R R; Smith, J; Weber, R; Trafford, J

    2014-01-01

    Increases in atmospheric CO2 cause the oceanic surface water to continuously acidify, which has multiple and profound impacts on coastal and continental shelf environments. Here we present the carbonate mineral composition in surface sediments from a range of continental shelf seabed environments and their current and predicted stability under ocean acidifying conditions. Samples come from the following four tropical Australian regions: (1) Capricorn Reef (southern end of the Great Barrier Reef), (2) the Great Barrier Reef Lagoon, (3) Torres Strait, and (4) the eastern Joseph Bonaparte Gulf. Beyond the near-shore zone, these regions typically have a carbonate content in surface sediments of 80 wt % or more. The abundance of high-magnesium calcites (HMC) dominates over aragonite (Arag) and low-magnesium calcite (LMC) and constitutes between 36% and 50% of all carbonate. HMC, with a magnesium content larger than 8-12 mol %, is more soluble than both Arag and LMC, and the solubility of HMC positively correlates with its magnesium concentration. From the solubility data of Plummer and Mackenzie ( Am. J. Sci. 1974 , 274 , 61 - 83 ), 95% of HMC in the four regions is presently in metastable equilibrium relative to global mean tropical sea surface water. HMC is predicted to become destabilized in the four regions between 2040 and 2080 AD, with typical HMC decline rates between 2% and 5% per year. The range of respective estimated carbonate dissolution rates is expected to exceed current continental shelf carbonate accumulation rates, leading to net dissolution of carbonate during the period of HMC decline. In a geological context, the decline in HMC in tropical continental shelf environments is a global event triggered by reaching below-equilibrium conditions. The characteristic change in carbonate mineral composition in continental shelf sediments will serve as a geological marker for the proposed Anthropocene Epoch. PMID:24972293

  13. Characteristics, generation and mass transport of nonlinear internal waves on the Washington continental shelf

    NASA Astrophysics Data System (ADS)

    Zhang, Shuang; Alford, Matthew H.; Mickett, John B.

    2015-02-01

    As a step toward better understanding the generation of nonlinear internal waves (NLIWs) on continental shelves and the factors determining their morphology, amplitude and propagation, we analyze more than 1500 NLIWs detected on the Washington (WA) continental shelf using four summer/fall time series of temperature and velocity measurements from a surface mooring deployed in 100 m of water. Propagating onshore toward the northeast, these NLIWs take a variety of forms, including internal solitary waves, solitary wave trains and bores. Nearly all are mode-1 depression waves that arrive semidiurnally along with the internal tide. The NLIW energy flux is correlated with the internal tide energy flux but not the local barotropic forcing, implying that the observed NLIWs arise primarily from shoaling remotely generated internal tides rather than local generation. Estimated onshore transport by the waves can equal or exceed offshore Ekman transport, suggesting the waves may play an important role in the mass balance on the continental shelf.

  14. Sources of phytoplankton to the inner continental shelf in the Santa Barbara Channel inferred from cross-shelf gradients in biological, physical and chemical parameters

    NASA Astrophysics Data System (ADS)

    Goodman, Jo; Brzezinski, Mark A.; Halewood, Elisa R.; Carlson, Craig A.

    2012-10-01

    Phytoplankton are a major food resource for filter-feeding organisms occupying intertidal and subtidal habitats of the inner continental shelf. Phytoplankton in these nearshore waters experience different anthropogenic and natural forcing compared to those offshore such that cross-shelf exchange would allow phytoplankton that were produced offshore to serve as a subsidy to inner shelf consumers when phytoplankton production on the shelf is negatively impacted. In the Santa Barbara Channel (SBC) the continental shelf is only a few kilometers wide facilitating exchange with offshore waters. Physical, chemical and biological gradients were examined monthly along a 3-km cross-shelf transect in the SBC from January, 2008 through April, 2009. Chemical and biological distributions followed temporal changes in physical forcing with higher nutrient concentrations and a more intense period of biological production associated with spring upwelling. Chlorophyll was relatively evenly distributed across the shelf during upwelling, but was present at higher concentrations on the inner shelf under stratified conditions. Similarly, cross-shelf gradients in the distribution of dominant phytoplankton genera were weakest during upwelling when blooms of the prymnesiophyte, Phaeocystis, and the diatoms, Eucampia spp. and Thalassiosira spp. occurred across most of the shelf. Upon stratification, blooms were largely confined to the inner shelf within 0.75 km of the shoreline with an initial bloom of the diatom Leptocylindrus spp. followed by Pseudo-nitzschia spp. and series of dinoflagellate blooms with Prorocentrum spp. and Lingulodinium spp. attaining the highest abundances. Phytoplankton taxonomic similarity decreased with increasing distance separating stations along the transect and was inversely related to stratification intensity. The observed distribution patterns and the trends in taxonomic similarity imply that for most of the year consumers within rocky intertidal and subtidal

  15. Splay faults and tsunamigenic sources across the continental shelf from 1964 great Alaska earthquake

    NASA Astrophysics Data System (ADS)

    Liberty, L. M.; Haeussler, P. J.; Moeller, M.

    2013-12-01

    Using tsunami run up, seismic reflection and bathymetric data, we identify tsunamigenic sea floor ruptures that resulted from the 1964 Great Alaska earthquake. These sea floor lineaments are rooted in megathrust splay faults that appear across the 500-km wide Gulf of Alaska continental shelf. Based on estimated tsunami travel times, we identify two splay faults that produced 5-10 m wave heights in the coastal town of Seward and remote settlements along the Kenai Peninsula. These faults splay from the megathrust along the trailing edge of the subducted Yakutat terrane that is sandwiched between the Pacific and North American plates. Duplexing along the megathrust likely transferred lateral motion along the decollement to vertical splay fault motion that resulted in multi-meter sea floor uplifts. We identify the Cape Cleare fault as the source of the earliest tsunami arrival for Seward, Puget Bay and Whidbey Bay. Sparker seismic data, pre- and post-earthquake bathymetry and crustal seismic data characterize the along-strike Holocene motion on this 70-km long fault that parallels the Patton Bay fault that ruptured on nearby Montague Island. We define a strand of the Middleton Island fault system as the source of the second arrival in Puget and Whidbey Bays and the earliest tsunami source on Middleton Island and other sites in the eastern Gulf of Alaska. Sea floor displacements of more than 20 m suggest both of these faults have repeatedly ruptured during Holocene earthquakes. Additionally, we identify a series of active thrust faults along the length of the Gulf of Alaska to Kodiak Island that likely initiated tsunami waves from smaller sea floor displacements. Sea floor offsets and splay faults that are mapped along the length of the continental shelf suggest Holocene coseismic rupture patterns are not reflected in interseismic GPS measurements along the Kenai Peninsula, but are consistent with seismic, tsunami, and geodetic measurements from the 1964 earthquake

  16. Sea-ice and surface water circulation, Alaskan continental shelf

    NASA Technical Reports Server (NTRS)

    Wright, F. F.; Sharma, G. D.; Burns, J. J. (Principal Investigator)

    1973-01-01

    The author has identified the following significant results. Over 1500 water samples from surface and from standard hydrographic depths were collected during June and July 1973 from Bering Sea and Gulf of Alaska. The measurement of temperature, salinity, and productivity indicated that various distinct water masses cover the Bering Sea Shelf. The suspended load in surface waters will be correlated with the ERTS-1 imagery as it becomes available to delineate the surface water circulation. The movement of ice floes in the Bering Strait and Bering Sea indicated that movement of ice varies considerably and may depend on wind stress as well as ocean currents.

  17. Structure of the North American Atlantic Continental Margin.

    ERIC Educational Resources Information Center

    Klitgord, K. K.; Schlee, J. S.

    1986-01-01

    Offers explanations on the origin of the North American Atlantic continental margin. Provides an analysis and illustrations of structural and strategraphic elements of cross sections of the Atlantic continental margin. Also explains the operations and applications of seismic-relection profiles in studying ocean areas. (ML)

  18. Sedimentary environments of inner Continental Shelf, west Florida

    SciTech Connect

    Donoghue, J.F. )

    1989-09-01

    Near-surface sediments of the Appalachia region of the west Florida shelf reflect a fluvial origin with strong evidence of reworking in a moderate-energy shallow marine environment. The inner shelf sediments are moderately sorted, fine quartz sands with only minor amounts of gravel and fines. High-resolution seismic records reveal a continual interplay of fluvial, deltaic, and nearshore environments during sea level fluctuations of the late Quaternary. Subsurface geomorphology includes large fluvial channels, prograding clinoforms, and ridge-and-swale topography. These relict features have been buried during the Holocene beneath a transgressive sand sheet with sediment supplied from mass nearshore shoals. The same source has contributed to the formation of a chain of barrier islands that forms a rim around the modern Apalachicola River delta. Barrier formation began approximately 3,000 years ago. Modern migration rates of the islands are high, in both landward and longshore directions, providing evidence for the rapid rate of transition from one type of sedimentary environment to another. The ample sedimentary supply appears at present to be keeping pace with moderate subsidence and sea level rise.

  19. Increased spatial variance accompanies reorganization of two continental shelf ecosystems.

    PubMed

    Litzow, Michael A; Urban, J Daniel; Laurel, Benjamin J

    2008-09-01

    Phase transitions between alternate stable states in marine ecosystems lead to disruptive changes in ecosystem services, especially fisheries productivity. We used trawl survey data spanning phase transitions in the North Pacific (Gulf of Alaska) and the North Atlantic (Scotian Shelf) to test for increases in ecosystem variability that might provide early warning of such transitions. In both time series, elevated spatial variability in a measure of community composition (ratio of cod [Gadus sp.] abundance to prey abundance) accompanied transitions between ecosystem states, and variability was negatively correlated with distance from the ecosystem transition point. In the Gulf of Alaska, where the phase transition was apparently the result of a sudden perturbation (climate regime shift), variance increased one year before the transition in mean state occurred. On the Scotian Shelf, where ecosystem reorganization was the result of persistent overfishing, a significant increase in variance occurred three years before the transition in mean state was detected. However, we could not reject the alternate explanation that increased variance may also have simply been inherent to the final stable state in that ecosystem. Increased variance has been previously observed around transition points in models, but rarely in real ecosystems, and our results demonstrate the possible management value in tracking the variance of key parameters in exploited ecosystems. PMID:18767612

  20. Large-scale penetration of Gulf Stream water onto the continental shelf north of Cape Hatteras

    NASA Technical Reports Server (NTRS)

    Gawarkiewicz, Glen; Church, Thomas M.; Luther, George W., III; Ferdelman, Timothy G.; Caruso, Michael

    1992-01-01

    The presence of Gulf Stream water on the continental shelf as much as 60 km north of Cape Hatteras was observed during a hydrographic cruise in the summer of 1990. Gulf Stream water was concentrated at mid-depth between 10 and 30 m and penetrated the shelfbreak front which normally separates the shelf water from slope water and Gulf Stream water. Velocities of Gulf Stream water in the upper 110 m of the water column along the 1000 m isobath indicated a flow of 18 to 25 cm/s directed towards the northwest. Gulf Stream water on the shelf is considered to be associated with low values of fluorescence, transmissivity, and nutrient concentrations relative to adjacent shelf water.

  1. Mean hydrography on the continental shelf from 26 repeat glider deployments along Southeastern Australia.

    PubMed

    Schaeffer, Amandine; Roughan, Moninya; Austin, Tim; Everett, Jason D; Griffin, David; Hollings, Ben; King, Edward; Mantovanelli, Alessandra; Milburn, Stuart; Pasquer, Benedicte; Pattiaratchi, Charitha; Robertson, Robin; Stanley, Dennis; Suthers, Iain; White, Dana

    2016-01-01

    Since 2008, 26 glider missions have been undertaken along the continental shelf of southeastern Australia. Typically these missions have spanned the continental shelf on the inshore edge of the East Australian Current from 29.5-33.5°S. This comprehensive dataset of over 33,600 CTD profiles from the surface to within 10 m of the bottom in water depths ranging 25-200 m provides new and unprecedented high resolution observations of the properties of the continental shelf waters adjacent to a western boundary current, straddling the region where it separates from the coast. The region is both physically and biologically significant, and is also in a hotspot of ocean warming. We present gridded mean fields for temperature, salinity and density, but also dissolved oxygen and chlorophyll-a fluorescence indicative of phytoplankton biomass. This data will be invaluable for understanding shelf stratification, circulation, biophysical and bio-geochemical interactions, as well as for the validation of high-resolution ocean models or serving as teaching material. PMID:27575831

  2. Mean hydrography on the continental shelf from 26 repeat glider deployments along Southeastern Australia

    PubMed Central

    Schaeffer, Amandine; Roughan, Moninya; Austin, Tim; Everett, Jason D.; Griffin, David; Hollings, Ben; King, Edward; Mantovanelli, Alessandra; Milburn, Stuart; Pasquer, Benedicte; Pattiaratchi, Charitha; Robertson, Robin; Stanley, Dennis; Suthers, Iain; White, Dana

    2016-01-01

    Since 2008, 26 glider missions have been undertaken along the continental shelf of southeastern Australia. Typically these missions have spanned the continental shelf on the inshore edge of the East Australian Current from 29.5–33.5°S. This comprehensive dataset of over 33,600 CTD profiles from the surface to within 10 m of the bottom in water depths ranging 25–200 m provides new and unprecedented high resolution observations of the properties of the continental shelf waters adjacent to a western boundary current, straddling the region where it separates from the coast. The region is both physically and biologically significant, and is also in a hotspot of ocean warming. We present gridded mean fields for temperature, salinity and density, but also dissolved oxygen and chlorophyll-a fluorescence indicative of phytoplankton biomass. This data will be invaluable for understanding shelf stratification, circulation, biophysical and bio-geochemical interactions, as well as for the validation of high-resolution ocean models or serving as teaching material. PMID:27575831

  3. Upper ocean variability in west Antarctic Peninsula continental shelf waters as measured using instrumented seals

    NASA Astrophysics Data System (ADS)

    Costa, Daniel P.; Klinck, John M.; Hofmann, Eileen E.; Dinniman, Michael S.; Burns, Jennifer M.

    2008-02-01

    Temperature profile data for the west Antarctic Peninsula (WAP) continental shelf waters, collected from freely ranging instrumented seals (crabeater, Lobodon carcinophagus and leopard, Hydrurga leptonyx), were used to demonstrate that these platforms can be used to supplement traditional oceanographic sampling methods to investigate the physical properties of the upper water column. The seal-derived profiles were combined with temperature profiles obtained from ship-based CTD measurements and from a numerical circulation model developed for the WAP to describe changes in temperature structure, heat content, and heat flux in the upper ocean waters of the WAP continental shelf. The seal-derived data documented the fall-to-winter transition of the surface waters and the shelf-wide presence of modified Circumpolar Deep Water (CDW) below 150-200 m on the WAP continental shelf. The heat content of the upper 200 m calculated from the seal-derived temperature profiles ranged between 1000 and 1500 MJ m -2; similar estimates were obtained from simulated temperature distributions. The seal-derived temperature measurements provided broader space and time resolution than was possible using any other currently available oceanographic sampling method. As such, the seal-derived measurements provided a valuable dataset for evaluation of temperature fields obtained from a numerical circulation model.

  4. A new bathymetry of the Northeast Greenland continental shelf: Constraints on glacial and other processes

    NASA Astrophysics Data System (ADS)

    Arndt, Jan Erik; Jokat, Wilfried; Dorschel, Boris; Myklebust, Reidun; Dowdeswell, Julian A.; Evans, Jeffrey

    2015-10-01

    A new digital bathymetric model (DBM) for the Northeast Greenland (NEG) continental shelf (74°N-81°N) is presented. The DBM has a grid cell size of 250 m × 250 m and incorporates bathymetric data from 30 multibeam cruises, more than 20 single-beam cruises and first reflector depths from industrial seismic lines. The new DBM substantially improves the bathymetry compared to older models. The DBM not only allows a better delineation of previously known seafloor morphology but, in addition, reveals the presence of previously unmapped morphological features including glacially derived troughs, fjords, grounding-zone wedges, and lateral moraines. These submarine landforms are used to infer the past extent and ice-flow dynamics of the Greenland Ice Sheet during the last full-glacial period of the Quaternary and subsequent ice retreat across the continental shelf. The DBM reveals cross-shelf bathymetric troughs that may enable the inflow of warm Atlantic water masses across the shelf, driving enhanced basal melting of the marine-terminating outlet glaciers draining the ice sheet to the coast in Northeast Greenland. Knolls, sinks, and hummocky seafloor on the middle shelf are also suggested to be related to salt diapirism. North-south-orientated elongate depressions are identified that probably relate to ice-marginal processes in combination with erosion caused by the East Greenland Current. A single guyot-like peak has been discovered and is interpreted to have been produced during a volcanic event approximately 55 Ma ago.

  5. Outer Continental shelf environmental assessment program. Final reports of principal investigators. Volume 51

    SciTech Connect

    Not Available

    1986-12-01

    The following are repoted: research to determine the accumulation of organic constituents and heavy metals from petroleum-impacted sediments by marine detritivores of the Alaskan outer continental shelf; Suspended particulate matter distribution, transport, and physical characteristics in the north Aleutian Shelf and St. George Basin lease areas; The production and dispersion of dissolved methane in southeastern Bering Sea; Oil spill vulnerability, coastal morphology, and sedimentation of outer Kenai Peninsula and Montague Island; Circulation and water masses in the Gulf of Alaska; Coastal oceanography of the northeastern Gulf of Alaska.

  6. Interpretation of seismic stratigraphy on the Amazon continental shelf

    SciTech Connect

    Alexander, C.R. Jr.; Nittrouer, C.A.; Demaster, D.J.

    1985-01-01

    The stratigraphy of the Amazon subaqueous delta has been examined using high-resolution reflection profiles. 15 piston cores from the Amazon Shelf were used to interpret the significance of the reflectors evident in the seismic profiles. Acoustic reflectors correlate with changes in grain size within cores, and generally represent coarser layers within the muddy deposits of the delta. Measurement of compressional-wave seismic velocity and saturated bulk density demonstrate that the correlation results from changes in acoustic impedance, caused by the grain-size variations. The reflectors reveal two predominant types of seismic stratigraphy: depositional and erosional. The depositional stratigraphy contains reflectors formed by relatively subtle change in grain size. Gently dipping topset and steeply dipping foreset demonstrate upward and seaward progradation of the subaqueous delta. This stratigraphy is truncated by erosional reflectors, which are significantly coarser layers. The erosional reflectors divide the depositional stratigraphy into distinct sets. The prevalence of erosional reflectors is greatest in the topset region near the river mouth, suggesting that sediment in this region, which is rapidly accumulating on 100-year time scales, has been eroded over longer time scales within the Holocene.

  7. Sea, ice and surface water circulation, Alaskan continental shelf

    NASA Technical Reports Server (NTRS)

    Sharma, G. D.; Wright, F. F.; Burns, J. J. (Principal Investigator)

    1973-01-01

    The author has identified the following significant results. ERTS-1 imagery has been extremely useful in understanding the tidal water movements in a large estuary such as Cook Inlet. As more imagery obtained during various tidal stages become available it appears that complex and fast changing micro-circulation patterns develop in various regions of Cook Inlet during each advancing and receding tide. More ERTS-1 synoptic imagery is needed to fully understand the effect of the approach of tidal front on the water movements in the various regions through the estuary. The conventional onboard ship data gathered during various cruises although revealed the overall circulation pattern in Cook Inlet but failed to show micro-subgyres which develop in various regions during each tide which are discernible on ther ERTS-1 imagery. Suspended load distribution in the Bering Sea during summer varies significantly. In areas of phytoplankton bloom and at the river mouths the suspended load is higher than the 1 mg/1 which is found over most areas. The influence of major rivers on temperature, salinity, and suspended load in surface water as well as at shallow depth is apparent. On the Bering shelf a strong pycnocline generally at depth 10-20 m is formed by surface fresh water flow which retains sediment in suspension over extended periods.

  8. Morphology and Dynamics of Subaqueous Dunes in a Tideless Outer Shelf (murcia Continental Shelf, Western Mediterranean Sea)

    NASA Astrophysics Data System (ADS)

    Durán, R.; Rivera, J.; Guillén, J.; de Cárdenas, E.; Muñoz, A.; Acosta, J.

    2014-12-01

    During the last years, the increasing application of multibeam sonar systems for mapping the seafloor has revealed the occurrence of sedimentary bedforms on the continental shelves worldwide. In addition, repeated multibeam surveys are used to monitor and compare the temporal evolution of such morphologies providing important insights into the sedimentary processes on the continental shelf. In the Murcia continental shelf, Western Mediterranean Sea, a large filed of subaqueous dunes has been observed in the middle and outer shelf. Here, we present a detailed morphologic and sedimentological analysis of these features with the aim to discuss their possible mechanism of formation and assess their potential mobility. The findings are based on swath-bathymetry collected using a SIMRAD EM 710 and EM3000D multibeam echosounders, high-resolution seismic profiles acquired with a TOPAS 018 system and sediment samples. Dunes are widely distributed between 60 and 110 m depth, from the Cope Cape, to the north, to the Águilas submarine canyon head rim, to the south. Dunes range from 18 to 140 m in wavelength and from 0.29 to 1.28 m in height. Dunes have asymmetrical profiles (average asymmetry of 0.065) with the lee slope facing towards the southwest that indicate a net south-westward sediment transport. Seabed samples collected in the crests and troughs of individual dunes show a similar grain-size distribution curve, but differ in the content of fines, which is higher in the trough, whereas the crests are dominated by coarse particles. High resolution seismic profiles reveal the presence of a continuous strong reflector that constitutes the base of the subaqueous dunes and could likely correspond to the Holocene transgressive ravinement surface.Dune migration rates were determined from the net displacement of the crests and troughs positions deduced from repeated multibeam surveys (2003 and 2013). Results indicate that the subaqueous dunes remain stationary or migrate at low

  9. Instabilities in nonlinear internal waves on the Washington continental shelf

    NASA Astrophysics Data System (ADS)

    Zhang, Shuang; Alford, Matthew H.

    2015-07-01

    Previous studies have identified two primary mechanisms (shear instability and convective instability) by which nonlinear internal waves (NLIWs) induce mixing on continental shelves. To determine the relative importance of these and their dependence on background flow conditions, we examine a much longer (6 month) data set from a moored ADCP/thermistor chain with 2 m vertical spacing in which over 600 NLIWs are detected. Turbulent properties of the 318 waves with detectable overturning instabilities are documented using Thorpe scales. The 130 waves detected while an ADCP was functioning are classified based on a Froude number criterion (Fr = uc, where u is velocity in the wave propagation direction, c is the wave phase speed). Of these, 108 waves are identified as shear-instability (Type I; Fr < 1) waves and 22 as convective instability (Type II; Fr > 1). Composites are constructed by averaging in a wave coordinate frame over all waves in each category, showing the mean spatial structure of dissipation and other wave quantities. Turbulence is highest at the sheared interface for Type I waves and throughout the wave core for Type II waves. No relationship between wave instability mechanisms and wave/background parameters such as wave steepness, stratification, or mean flow is found, except that unstable waves tend to be more energetic, demonstrating a need to better understand wave propagation and breaking in complex and variable coastal oceanographic background flows.

  10. Water exchange between the continental shelf and the cavity beneath Nioghalvfjerdsbræ (79 North Glacier)

    NASA Astrophysics Data System (ADS)

    Wilson, N. J.; Straneo, F.

    2015-09-01

    The mass loss at Nioghalvfjerdsbræ is primarily due to rapid submarine melting. Ocean data obtained from beneath the Nioghalvfjerdsbræ ice tongue show that melting is driven by the presence of warm (1°C) Atlantic Intermediate Water (AIW). A sill prevents AIW from entering the cavity from Dijmphna Sund, requiring that it flow into the cavity via bathymetric channels to the south at a pinned ice front. Comparison of water properties from the cavity, Dijmphna Sund, and the continental shelf support this conclusion. Overturning circulation rates inferred from observed melt rates and cavity stratification suggest an exchange flow between the cavity and the continental shelf of 38mSv, sufficient to flush cavity waters in under 1 year. These results place upper bounds on the timescales of external variability that can be transmitted to the glacier via the ice tongue cavity.

  11. The influence of surface waves on water circulation in a mid-Atlantic continental shelf region

    NASA Technical Reports Server (NTRS)

    Whitlock, C. H.; Talay, T. A.

    1974-01-01

    The importance of wave-induced currents in different weather conditions and water depths (18.3 m and 36.6 m) is assessed in a mid-Atlantic continental-shelf region. A review of general circulation conditions is conducted. Factors which perturb the general circulation are examined using analytic techniques and limited experimental data. Actual wind and wave statistics for the region are examined. Relative magnitudes of the various currents are compared on a frequency of annual occurrence basis. Results indicated that wave-induced currents are often the same order of magnitude as other currents in the region and become more important at higher wind and wave conditions. Wind-wave and ocean-swell characteristics are among those parameters which must be monitored for the analytical computation of continental-shelf circulation.

  12. An oilspill risk analysis for the North Atlantic outer continental shelf lease area

    USGS Publications Warehouse

    Smith, Richard Allmon; Slack, James Richard; Davis, Robert K.

    1976-01-01

    The Federal Government has proposed to lease 1,172,795 acres of Outer Continental Shelf (OCS) lands on Georges Bank off the New England Coast for oil and gas development. Estimated recoverable petroleum resources for the proposed 206 tract sale area range from 180 to 650 million barrels. Contingent upon actual discovery of this quantity of oil, production is expected to span a period of about 20 years. An oilspill risk analysis was conducted to determine relative environmental hazards of developing oil in the North Atlantic Outer Continental Shelf lease area. The study analyzed probability of spill occurrence, likely path of pollutants from spills, and locations in space and time of recreational and biological resources likely to be vulnerable. These results are combined to yield estimates of the overall oilspill risk associated with development of the lease area. (Woodard-USGS)

  13. Adequacy of environmental information for outer continental shelf oil and gas decisions: Georges Bank. Final report

    SciTech Connect

    Not Available

    1991-01-01

    Georges Bank, a large, shallow marine bank with important fishery resources and possibly important oil and gas resources, lies east of Massachusetts in the territorial waters of both the United States and Canada. The Department of the Interior has planned since 1974 to lease parts of the north Atlantic outer continental shelf (OCS)--including part of Georges Bank--for oil and gas exploration. As a result of public concern about the environmental impacts of oil and gas production on the U.S. OCS, Congress declared a moratorium on drilling on Georges Bank and an area to the southwest. The report--by the NRC's Committee to Review the Outer Continental Shelf Environmental Studies Program and its panels on physical oceanography, ecology, and socioeconomics--reviews the adequacy of information bearing on the potential environmental impacts of OCS oil and gas activities for the Georges Bank sale area.

  14. Bottom stress estimates and sand transport on northern California inner continental shelf

    USGS Publications Warehouse

    Cacchione, D.A.; Drake, D.E.; Ferreira, J.T.; Tate, G.B.

    1994-01-01

    Measurements of velocities and light transmission in the bottom boundary layer on the continental shelf off northern California demonstrate the importance of storms in the transport of sediment along the coast and offshore in this region. Time-series estimates of bottom stress obtained from a combined wave-current bottom boundary layer model in which wave and current measurements from the Geoprobe tripod were used as input show high stress values of 10 dynes cm-2 during two distinct storm events in early February and early March, 1991. These stresses induce significant offshore sediment transport, achieving maximum values of about 0.5 g cm-1 s-1. The net transport over the entire measurement period from 30 January 1991 to 13 March 1991 was along the coast toward the north and offshore. This transport pattern explains slow migration of low amplitude, broad crescentic dunes along and across this portion of the inner continental shelf. ?? 1994.

  15. [Circulation and exchange processes on the South Atlantic Bight Continental Shelf]. [Progress summary for 1986

    SciTech Connect

    Not Available

    1986-12-31

    A continuation of the physical oceanography program to investigate circulation and exchange processes on the South Atlantic Bight (SAB) Continental Shelf is proposed. The transport and dispersal of materials entering the inner shelf zone with river discharge is not well understood at present. Climatological data, satellite imagery, and numerical modeling results indicate two removal routes for these nearshore waters: northeast transport and offshore exchange between Cape Fear and Savannah during the spring and summer when maximum run-off and northward winds prevail; and southward transport and offshore exchange near Cape Canaveral during the fall when southward winds prevail. We have conducted interdisciplinary experiments to investigate the transport processes in the inner to outer shelf between Savannah, Georgia and Cape Fear, North Carolina. In addition we propose to continue synthesis and interpretation of current measurements. The analyses will focus on determining the coupling mechanisms of inner shelf and outer shelf waters with special emphasis placed on resolving the modes and rates of shelf water removal.

  16. High Resolution Quaternary Seismic Stratigraphy of the New York Bight Continental Shelf

    USGS Publications Warehouse

    Schwab, William C.; Denny, J.F.; Foster, D.S.; Lotto, L.L.; Allison, M.A.; Uchupi, E.; Swift, B.A.; Danforth, W.W.; Thieler, E.R.; Butman, Bradford

    2003-01-01

    A principal focus for the U.S. Geological Survey (USGS) Coastal and Marine Geology Program (marine.usgs.gov) is regional reconnaissance mapping of inner-continental shelf areas, with initial emphasis on heavily used areas of the sea floor near major population centers. The objectives are to develop a detailed regional synthesis of the sea-floor geology in order to provide information for a wide range of management decisions and to form a basis for further investigations of marine geological processes. In 1995, the USGS, in cooperation with the U.S. Army Corps of Engineers (USACOE), New York District, began to generate reconnaissance maps of the continental shelf seaward of the New York - New Jersey metropolitan area. This mapping encompassed the New York Bight inner-continental shelf, one of the most heavily trafficked and exploited coastal regions in the United States. Contiguous areas of the Hudson Shelf Valley, the largest physiographic feature on this segment of the continental shelf, also were mapped as part of a USGS study of contaminated sediments (Buchholtz ten Brink and others, 1994; 1996). The goal of the reconnaissance mapping was to provide a regional synthesis of the sea-floor geology in the New York Bight area, including: (a) a description of sea-floor morphology; (b) a map of sea-floor sedimentary lithotypes; (c) the geometry and structure of the Cretaceous strata and Quaternary deposits; and (d) the geologic history of the region. Pursuing the course of this mapping effort, we obtained sidescan-sonar images of 100 % of the sea floor in the study area. Initial interpretations of these sidescan data were presented by Schwab and others, (1997a, 1997b, 2000a). High-resolution seismic-reflection profiles collected along each sidescan-sonar line used multiple acoustic sources (e.g., watergun, CHIRP, Geopulse). Multibeam swath-bathymetry data also were obtained for a portion of the study area (Butman and others, 1998;). In this report, we present a series

  17. Benthic foraminifers from the continental shelf and slope of the Gulf of Mexico: An indicator of shelf hypoxia

    USGS Publications Warehouse

    Osterman, L.E.

    2003-01-01

    Benthic foraminifers from 74 core-top sediment samples collected primarily from the continental shelf of the Gulf of Mexico were analyzed to determine a microfaunal indicator for shelf hypoxia to be used in future paleoenvironmental studies. Principal component analysis (PCA) and cluster analysis (CA) of 93 species recognized factors/clusters that were similar to previous investigations of the benthic foraminifers, except that both analyses also identified PCA6/CA6 in the area where hypoxic conditions have been observed. Three low-oxygen-tolerant species, Pseudononion atlanticum, Epistominella vitrea, and Buliminella morgani have high factor loadings in PCA6. The cumulative percentage of three species is defined as the PEB (PEB, Pseudononion, Epistominella, Buliminella) index. The highest PEB values observed in the 74 surface sediment samples occur in the zone of recognized hypoxia on the Louisiana shelf. Values of the PEB index are also elevated along the southern Texas coastline, suggesting that this area may experience periodic hypoxia as well. ?? 2003 Elsevier Ltd. All rights reserved.

  18. Transport and transfer rates in the waters of the continental shelf. Annual report

    SciTech Connect

    Biscaye, P.E.

    1980-09-01

    The goal of govern project is to understand and quantify the processes that the transport and dispersal of energy-related pollutants introduced to the waters of the continental shelf and slope. The report is divided into sections dealing with processes associated with suspended solids; processes associated with sediments sinks for radionuclides and other pollutants; and spreading of water characteristics and species in solution. (ACR)

  19. Outer continental shelf, Beaufort Sea, oil and gas lease sale 170 (proposed notice of sale)

    SciTech Connect

    1997-12-31

    The Minerals Management Service (MMS) is issuing this proposed Notice of Sale under the Outer Continental Shelf (OCS) Lands Act (43 U.S.C. 1331-1356, as amended) and the regulations issued thereunder (30 CFR Part 256). A `Sale Notice Package,` containing this Notice and several supporting and essential documents referenced in the Notice, is available from the MMS Alaska OCS Regional Office Public Information Unit.

  20. Oil and gas developments in Atlantic Coastal Plain and Outer Continental Shelf in 1985 and 1986

    SciTech Connect

    Amato, R.V.

    1987-10-01

    Drilling activity for 1985 was not reported previously due to the low level of activity. No exploratory drilling took place on the Atlantic outer continental shelf in 1985 or 1986. One shallow well was drilled onshore in Georgia on the Atlantic coastal plan in 1985, and 2 wells were completed in Georgia in 1986. Texaco drilled 6 core holes on the Virginia coastal plain in 1986. 2 tables.

  1. An oilspill risk analysis for the Mid-Atlantic Outer Continental Shelf lease area

    USGS Publications Warehouse

    Smith, Richard Allmon; Slack, James Richard; Davis, Robert K.

    1976-01-01

    An oilspill risk analysis was conducted to determine relative environmental impacts of developing oil in different regions of the Mid-Atlantic Outer Continental Shelf lease area. The study analyzed probability of spills, likely path of pollutants from spills, and locations in space and time of recreational and biological resources likely to be vulnerable. These results are combined to yield estimates of the overall oilspill risk associated with development of the lease area. (Woodard-USGS)

  2. Hydrothermal origin of oil and gas reservoirs in basement rock of the South Vietnam continental shelf

    SciTech Connect

    Dmitriyevskiy, A.N.; Kireyev, F.A.; Bochko, R.A.; Fedorova, T.A. )

    1993-07-01

    Oil-saturated granites, with mineral parageneses typical of hydrothermal metasomatism and leaching haloes, have been found near faults in the crystalline basement of the South Vietnam continental shelf. The presence of native silver, barite, zincian copper, and iron chloride indicates a deep origin for the mineralizing fluids. Hydrothermally altered granites are a new possible type of reservoir and considerably broaden the possibilities of oil and gas exploration. 15 refs., 22 figs., 1 tab.

  3. Megaflutes in a continental shelf setting, Placentia Bay, Newfoundland

    NASA Astrophysics Data System (ADS)

    Shaw, John; Puig, Pere; Han, Guoqi

    2013-05-01

    Megaflutes - erosional scours normally found in deep water on continental slopes - were identified in 1978 on sidescan sonograms and seismic reflection profiles from Placentia Bay on the south coast of Newfoundland, Canada. Data from recent extensive multibeam sonar surveys provide an opportunity to describe the morphology and distribution of the megaflutes in detail, and to consider the formative processes. They occur on the east side of the outer bay, at a depth of ~ 200 m, in a 2-3 km-wide swath that continues to the south into Halibut Channel, over a total distance of ~ 100 km. The megaflutes have been formed by removal of a layer of postglacial mud, exposing underlying glaciomarine sediments and releasing a volume of 4.5 km3. They occur in a range of forms, including single, multiple, and coalescent types, and in some areas at least their inception was related to pre-existing pockmarks. Radiocarbon dates from piston cores are used to demonstrate that megaflute formation post-dated ca. 9 ka. Megaflute formation in Placentia Bay has been attributed to a 'reverse flow' from the tsunami generated by the 1929 Grand Banks earthquake, and this is still the accepted hypothesis. We argue that the return flow from a tsunami did not generate the megaflutes, and suggest instead that they could be formed during south-flowing density currents generated when volumes of cold saline water stored in the deep (> 250 m) basins at the head of Placentia Bay are intermittently displaced and spilled south in a shallow channel at the east side of the bay after intense coastal surface dense water formation events, perhaps during very cold winters.

  4. Atlantic water variability on the SE Greenland continental shelf and its relationship to SST

    NASA Astrophysics Data System (ADS)

    Sutherland, D. A.; Straneo, F.; Rosing-Asvid, A.; Stenson, G.; Davidson, F. J.; Hammill, M.

    2012-12-01

    Interaction of warm, Atlantic-origin water (AW) and colder, polar origin water (PW) advecting southward in the East Greenland Current (EGC) influences the heat content of water entering Greenland's outlet glacial fjords. Here we use depth and temperature data derived from deep-diving seals to map out water mass variability across the continental shelf and to augment existing bathymetric products. We find two dominant modes in the vertical temperature structure: a cold mode, with the typical AW/PW layering observed in the EGC, and a warm mode, where AW is present throughout the water column. The prevalence of these modes varies seasonally and spatially across the continental shelf, implying distinct AW pathways. In addition, we find that satellite sea surface temperatures (SST) correlate significantly with temperatures in the upper 50 m (R=0.54), but this correlation decreases with depth (R=0.22 at 200 m), and becomes insignificant below 250 m. Thus, care must be taken in using SST as a proxy for heat content, as AW mainly resides in these deeper layers. Regional map showing the location of all seal tracks originating from Canada and Greenland (stars). Tracks passing inside (red) or outside (blue) the SE Greenland region (black) were subdivided into continental shelf regions (green boxes) near Sermilik Fjord (SF), Cape Farewell (CF) and Kangerdlugssuaq Fjord (KG). GEBCO bathymetry is contoured at 200, 1000, 2000, and 3000 m.

  5. Temporal coherence of the acoustic field forward propagated through a continental shelf with random internal waves.

    PubMed

    Gong, Zheng; Chen, Tianrun; Ratilal, Purnima; Makris, Nicholas C

    2013-11-01

    An analytical model derived from normal mode theory for the accumulated effects of range-dependent multiple forward scattering is applied to estimate the temporal coherence of the acoustic field forward propagated through a continental-shelf waveguide containing random three-dimensional internal waves. The modeled coherence time scale of narrow band low-frequency acoustic field fluctuations after propagating through a continental-shelf waveguide is shown to decay with a power-law of range to the -1/2 beyond roughly 1 km, decrease with increasing internal wave energy, to be consistent with measured acoustic coherence time scales. The model should provide a useful prediction of the acoustic coherence time scale as a function of internal wave energy in continental-shelf environments. The acoustic coherence time scale is an important parameter in remote sensing applications because it determines (i) the time window within which standard coherent processing such as matched filtering may be conducted, and (ii) the number of statistically independent fluctuations in a given measurement period that determines the variance reduction possible by stationary averaging. PMID:24180758

  6. Resuspended sediments can contribute to the establishment and maintenance of hypoxia on the Louisiana continental shelf - Eldridge

    EPA Science Inventory

    Hypoxia occurs during summer on the Louisiana Continental Shelf. We investigated whether resuspension of sediment organic matter and the reduced end products of anaerobic microbial metabolism contributes to the onset and maintenance of hypoxia. The potential oxygen demand due to...

  7. Spatiotemporal chlorophyll-a dynamics on the Louisiana continental shelf derived from a dual satellite imagery algorithm

    EPA Science Inventory

    A monthly time series of remotely sensed chlorophyll-a (Chlars) over the Louisiana continental shelf (LCS) was developed and examined for its relationship to river discharge, nitrate concentration, total phosphorus concentration, photosynthetically available radiation (PAR), wind...

  8. Impact of Satellite Remote Sensing Data on Simulations of Coastal Circulation and Hypoxia on the Louisiana Continental Shelf

    EPA Science Inventory

    We estimated surface salinity flux and solar penetration from satellite data, and performed model simulations to examine the impact of including the satellite estimates on temperature, salinity, and dissolved oxygen distributions on the Louisiana continental shelf (LCS) near the ...

  9. 75 FR 17156 - Gulf of Mexico, Outer Continental Shelf, Western Planning Area, Oil and Gas Lease Sale 215 (2010...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-04-05

    ... Minerals Management Service Gulf of Mexico, Outer Continental Shelf, Western Planning Area, Oil and Gas Lease Sale 215 (2010) Environmental Assessment AGENCY: Minerals Management Service, Interior. ACTION: Notice of availability of an environmental assessment. SUMMARY: The Minerals Management Service (MMS)...

  10. Trace metal distribution in sediments of northern continental shelf of Crete Island, Eastern Mediterranean

    NASA Astrophysics Data System (ADS)

    Poulos, S. E.; Dounas, C. G.; Alexandrakis, G.; Koulouri, P.; Drakopoulos, P.

    2009-08-01

    The present study investigates the distribution of trace metals (Zn, Hg, Cd, Cu, and Pb), as indicators of pollution, in the surficial offshore shelf sediments along the northern coast of Heraklion Prefecture (Crete, Mediterranean Sea). The concentrations and the spatial distribution of the different trace metals, in relation to the sedimentological characteristics and the water circulation pattern of the entire continental shelf, are associated with human inshore sources of pollutants located along the coastline of the study area. Although the trace metal concentrations measured are higher than the background values, they are not considered to be dangerous to human health, as they are lower than the standard values given by the World Health Organisation, with only a few localised exceptions. Furthermore, results reveal the important role of local hydrodynamism that moves fine-grained material and associated trace metals offshore (seawards to wave breaking zone) and then transports them eastwards by entrapping them in the prevailing offshore shelf-water circulation.